Circumferential Seal with Bifurcated Flow along Multi-Axis Stepped Grooves

ABSTRACT

A circumferential seal assembly capable of dividing a gas into separate flow paths before communication between a rotatable runner and a pair of seal rings is presented. The assembly includes an annular seal housing, a rotatable runner, a pair of annular seal rings, and a plurality of groove structures. Each groove structure separates a source flow communicated into a feed groove so that a portion enters at least two grooves to form a longitudinal flow therein. Each groove includes at least two adjoining steps defined by base walls. The base walls are arranged along the groove to decrease depthwise opposite to rotation of the rotatable runner. Two adjoining base walls are disposed about a base shoulder. Each base shoulder locally redirects the longitudinal flow to form an outward radial flow in the direction of one annular seal ring. The base walls are bounded by and intersect a pair of side walls. Each side wall includes at least one side shoulder which narrows the groove widthwise and locally redirects the longitudinal flow away from the side wall to form a lateral flow in the direction of the other side wall. Each reduction to the volume of the gas at the downstream end of each groove structure increases pressure and enhances the stiffness of a thin-film layer between each annular seal ring and the rotatable runner.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 15/899,813 filed Feb. 20, 2018 which is a continuation of U.S.patent application Ser. No. 14/845,947 filed Sep. 4, 2015 now U.S. Pat.No. 9,970,482 which is a continuation-in-part of U.S. patent applicationSer. No. 14/396,101 filed Oct. 22, 2014 now U.S. Pat. No. 9,194,424which is a National Phase of PCT Application No. PCT/US2014/033736 filedApr. 11, 2014 which further claims priority from U.S. ProvisionalApplication No. 61/811,900 filed Apr. 15, 2013, each entitledCircumferential Back-to-Back Seal Assembly with Bifurcated Flow. Thesubject matters of the prior applications are incorporated in theirentirety herein by reference thereto.

FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

None.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention generally relates to a circumferential seal assembly withbifurcated hydrodynamic flow for use within a gas turbine engine andmore particularly is concerned, for example, with a pair of annular sealrings separately disposed within an annular seal housing about arotatable runner attached to a shaft, wherein the runner furtherincludes a plurality of hydrodynamic grooves with bothlaterally-disposed steps and vertically-disposed steps which separateand direct flow onto the annular seal rings to form a pair of thin-filmlayers sealing one compartment from another compartment.

2. Background

Turbine engines typically include a housing with a plurality ofcompartments therein and a rotatable shaft that passes through adjoiningcompartments separately including a gas and a lubricant. Leakage of alubricant from one compartment into another compartment containing a gascould adversely affect performance and function of a gas turbine.Leakage of a gas from one compartment into another compartmentcontaining a lubricant is likewise detrimental. As such, adjoiningcompartments must be isolated from one another by means of a sealingsystem that prevents one fluid, either a lubricant or a gas, frommigrating along a rotatable shaft and entering a compartment so as tomix with another fluid therein.

In the case of an aircraft engine, leakage of a lubricant or a gasacross a seal into a neighboring compartment may cause oil coking or anengine fire. Oil coke is a byproduct formed when an oil lubricant and agas mix at a temperature that chemically alters the oil. Oil coke canfoul sealing surfaces thereby degrading bearing lubrication andimpairing the integrity of a seal. It is important in similarapplications, not just aircraft engines, that a lubricant be isolatedwithin a lubricant sump and that a seal around a rotating shaft notallow a lubricant to escape the sump or a hot gas to enter the sump.Many applications will include either a circumferential seal or a faceseal to prevent mixing of an oil lubricant and a hot gas; however,circumferential shaft seals are the most widely used under theabove-noted conditions.

Various circumferential seal systems are employed within the art to forma seal between a compartment containing a gas at a high pressure and acompartment containing an oil lubricant at a low pressure. Sealingsystems typically include grooves disposed along an inner annularsurface of a seal ring to form a thin-film layer between the seal ringand a shaft.

Presently known circumferential seal designs are particularlyproblematic when the pressure differential is low. The absence of asignificant pressure differential between compartments does not permitformation of a thin-film layer adequately capable of preventingmigration of a fluid along the interface between a seal ring and ashaft.

Presently known circumferential seal designs are further problematicwhen used in conjunction with a translatable runner. The temperaturesand/or mechanical loads within a turbine engine often cause a runner,and sealing surface thereon, to translation along the axial dimension ofan engine. The result is a sealing interface that is difficult tooptimize over the operational range of a turbine engine.

Accordingly, what is required is a circumferential seal assemblyinterposed between a pair of compartments that minimizes degradation toand/or failure of a seal between a rotatable runner and a pair of sealelements.

SUMMARY OF THE INVENTION

An object of the invention is to provide a circumferential seal assemblyinterposed between a pair of compartments that minimizes degradation toand/or failure of a seal between a rotatable runner and a pair of sealelements.

In accordance with embodiments of the invention, the circumferentialseal assembly includes an annular seal housing, a rotatable runner, apair of annular seal rings, and a plurality of groove structures. Theannular seal housing is disposed between a pair of compartments. Theannular seal rings are disposed within the annular seal housing anddisposed about the rotatable runner. The groove structures are disposedalong an outer annular surface of the rotatable runner. Each groovestructure includes at least two grooves intersecting a feed groove. Thegroove structure separates a source flow communicated into the feedgroove so that a portion of the source flow enters each groove to form alongitudinal flow therein. Each groove includes at least two adjoiningsteps whereby each step is defined by a base wall. The base walls arearranged along the groove to decrease depthwise in the directionopposite to rotation of the rotatable runner. Two adjoining base wallsare disposed about a base shoulder. Each base shoulder locally redirectsthe longitudinal flow to form an outward radial flow in the direction ofone annular seal ring. The base walls are bounded by and intersect apair of side walls. Each side wall includes at least one side shoulderwhich narrows the groove widthwise and locally redirects thelongitudinal flow away from the side wall to form a lateral flow in thedirection of the other side wall.

In accordance with other embodiments of the invention, one side shoulderalong each side wall intersects one base shoulder so that the outwardradial flow and the lateral flows interact.

In accordance with other embodiments of the invention, one base shoulderis disposed between a pair of side shoulders along each side wall.

In accordance with other embodiments of the invention, two sideshoulders upstream of a base shoulder are disposed in an opposedarrangement.

In accordance with other embodiments of the invention, two sideshoulders downstream of a base shoulder are disposed in an opposedarrangement.

In accordance with other embodiments of the invention, two sideshoulders upstream of a base shoulder are disposed in an offsetarrangement.

In accordance with other embodiments of the invention, two sideshoulders downstream of a base shoulder are disposed in an offsetarrangement.

In accordance with other embodiments of the invention, one side shoulderalong each side wall is disposed upstream from a base shoulder.

In accordance with other embodiments of the invention, one side shoulderalong each side wall is disposed downstream from a base shoulder.

In accordance with other embodiments of the invention, one side shoulderintersects a base shoulder.

In accordance with other embodiments of the invention, the base shoulderis disposed between two other side shoulders.

In accordance with other embodiments of the invention, two other sideshoulders are disposed along one side wall and a side shoulder disposedalong another side wall intersects a base shoulder.

In accordance with other embodiments of the invention, one of two otherside shoulders is disposed along the same side wall as a side shoulderwhich intersects the base shoulder.

In accordance with other embodiments of the invention, a depth of eachof two side shoulders are equal.

In accordance with other embodiments of the invention, a depth of eachof two side shoulders differ.

In accordance with other embodiments of the invention, a depth of eachof one side shoulder and one base shoulder differ.

In accordance with other embodiments of the invention, a depth of eachof one side shoulder and one base shoulder are equal.

In accordance with other embodiments of the invention, at least one basewall is tapered.

In accordance with other embodiments of the invention, at least one sidewall is tapered.

In accordance with other embodiments of the invention, base walls andside walls are tapered.

In accordance with method embodiments of the invention, a method forforming a thin-film layer between a pair of annular seal rings and arotatable runner is provided by communicating, separating, andredirecting steps. A source flow is communicated into a feed groovefurther communicable with at least two grooves. Each groove has anupstream end, at the intersection between the groove and the feedgroove, and a downstream end. The source flow is separated at theupstream ends into each groove to form a longitudinal flow therein. Thelongitudinal flow is redirected via interaction with a base shoulderinterposed between a pair of base walls to form an outward radial flowadjacent to the base shoulder. The base walls are disposed between apair of side walls. The base walls are arranged along the groove todecrease depthwise in the direction opposite to rotation of therotatable runner. The longitudinal flow is redirected via interactionwith a side shoulder along at least one side wall to form a lateral flowin the direction of another side wall. The lateral flow and the outwardradial flow are perpendicular to one another and to the longitudinalflow.

In accordance with other method embodiments of the invention, the methodfurther includes the step of converging at least one lateral flow withthe outward radial flow when at least one side shoulder intersects thebase shoulder whereby the side shoulder(s) and the base shoulder arealigned along a plane that traverses a groove. The converging stepenhances the stiffness of a thin-film layer between each annular sealring and the rotatable runner.

In accordance with other method embodiments of the invention, at leastone lateral flow is formed downstream from an outward radial flow.

In accordance with other method embodiments of the invention, at leastone lateral flow is formed upstream from an outward radial flow.

In accordance with other method embodiments of the invention, the methodfurther includes the step of converging the lateral flow from one sidewall with another lateral flow from another side wall when the sideshoulders are disposed in an opposed arrangement whereby the sideshoulders are aligned along a plane that traverses the groove. Theconverging step enhances the stiffness of a thin-film layer between eachannular seal ring and the rotatable runner.

In accordance with other method embodiments of the invention, the methodfurther includes the step of impinging one side wall by the lateral flowformed by the side shoulder along another side wall. The impinging stepenhances the stiffness of a thin-film layer between each annular sealring and the rotatable runner.

Several exemplary advantages are mentionable. The invention facilitatesa circumferential seal along a rotatable/translatable runner between apair of lower pressure compartments that minimizes mixing of a lubricantand a gas within adjacent compartments. The invention facilitates acircumferential seal along a rotatable/translatable runner between apair of compartments that minimizes translational effects on sealingproperties. The invention minimizes contamination to a pairedarrangement of annular seal rings by a lubricant originating from acompartment. The invention minimizes wear along a back-to-backarrangement of sealing rings within a seal assembly.

The invention may be used within a variety of applications wherein asealing assembly including a pair of annular seals is disposed about atranslatable sealing surface between a pair of low pressurecompartments. One specific non-limiting example is a turbine enginewherein a seal assembly is disposed about a rotatable/translatablerunner.

The above and other objectives, features, and advantages of thepreferred embodiments of the invention will become apparent from thefollowing description read in connection with the accompanying drawings,in which like reference numerals designate the same or similar elements.

BRIEF DESCRIPTION OF THE DRAWINGS

Additional aspects, features, and advantages of the invention will beunderstood and will become more readily apparent when the invention isconsidered in the light of the following description made in conjunctionwith the accompanying drawings.

FIG. 1 is an enlarged cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a gapwithin a seal housing disposed about a runner attached to a shaft (crosssection of annular seal assembly below centerline, runner, and shaft notshown) rotatable about a centerline within a turbine engine inaccordance with an embodiment of the invention.

FIG. 2 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a gapwithin a seal housing disposed about a rotatable runner attached to ashaft (cross section of annular seal assembly below runner and shaft notshown) wherein an outer annular surface along the runner includes aplurality of groove structures separately disposed thereon whereby eachgroove includes at least two steps and each groove structurecommunicates with both seal rings in accordance with an embodiment ofthe invention.

FIG. 3 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a gapwithin a seal housing disposed about a rotatable runner attached to ashaft (cross section of annular seal assembly below runner and shaft notshown) wherein an outer annular surface along the runner includes aplurality of groove structures communicable with a single annular groovethereon whereby each groove includes at least two steps and each groovestructure communicates with both seal rings in accordance with anembodiment of the invention.

FIG. 4 is an enlarged cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a centerring within a seal housing disposed about a runner attached to a shaft(cross section of annular seal assembly below centerline, runner, andshaft not shown) rotatable about a centerline within a turbine engine inaccordance with an embodiment of the invention.

FIG. 5 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a centerring within a seal housing disposed about a rotatable runner attached toa shaft (cross section of annular seal assembly below runner and shaftnot shown) wherein an outer annular surface along the runner includes aplurality of groove structures separately disposed thereon whereby eachgroove includes at least two steps and each groove structurecommunicates with both seal rings in accordance with an embodiment ofthe invention.

FIG. 6 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a centerring within a seal housing disposed about a rotatable runner attached toa shaft (cross section of annular seal assembly below runner and shaftnot shown) wherein an outer annular surface along the runner includes aplurality of bifurcated groove structures separately disposed thereonwhereby each groove includes at least two steps and each pair ofnon-intersecting groove structures communicates with both seal rings inaccordance with an embodiment of the invention.

FIG. 7 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a centerring within a seal housing disposed about a rotatable runner attached toa shaft (cross section of annular seal assembly below runner and shaftnot shown) wherein an outer annular surface along the runner includes aplurality of bifurcated multi-groove structures separately disposedthereon whereby each groove includes at least two steps and each pair ofnon-intersecting multi-groove structures communicates with both sealrings in accordance with an embodiment of the invention.

FIG. 8 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a centerring within a seal housing disposed about a rotatable runner attached toa shaft (cross section of annular seal assembly below runner and shaftnot shown) wherein an outer annular surface along the runner includes aplurality of multi-groove structures separately disposed thereon wherebyeach groove includes at least two steps and each multi-groove structurecommunicates with both seal rings in accordance with an embodiment ofthe invention.

FIG. 9 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a centerring within a seal housing disposed about a rotatable runner attached toa shaft (cross section of annular seal assembly below runner and shaftnot shown) wherein an outer annular surface along the runner includes aplurality of bifurcated multi-groove structures separately disposedthereon whereby the multi-grooves form two separate substructures withineach multi-groove structure, each groove includes at least two steps,and each multi-groove structure communicates with both seal rings inaccordance with an embodiment of the invention.

FIG. 10 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a gapwithin a seal housing with an optional windback thread disposed about arotatable runner attached to a shaft (cross section of annular sealassembly and runner below centerline and shaft not shown) and optionalslots positioned along one end of the rotatable runner adjacent to thewindback thread wherein an outer annular surface along the runnerincludes a plurality of multi-groove structures separately disposedthereon whereby each groove includes at least two steps and eachmulti-groove structure communicates with both seal rings in accordancewith an embodiment of the invention.

FIG. 11 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a gapwithin a seal housing with an optional windback thread disposed about arotatable runner attached to a shaft (cross section of annular sealassembly and runner below centerline and shaft not shown) and optionalslots positioned along one end of the rotatable runner adjacent to thewindback thread wherein an outer annular surface along the runnerincludes a plurality of multi-groove structures separately disposedthereon whereby the grooves are tapered, each groove includes at leasttwo steps, and each multi-groove structure communicates with both sealrings in accordance with an embodiment of the invention.

FIG. 12 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a gapwithin a seal housing with an optional windback thread disposed about arotatable runner attached to a shaft (cross section of annular sealassembly and runner below centerline and shaft not shown) wherein anouter annular surface along the runner includes a plurality ofmulti-groove structures separately disposed thereon whereby the width ofadjacent multi-groove structures vary, each groove includes at least twosteps, and each multi-groove structure communicates with both seal ringsin accordance with an embodiment of the invention.

FIG. 13 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a gapwithin a seal housing with an optional windback thread disposed about arotatable runner attached to a shaft (cross section of annular sealassembly and runner below centerline and shaft not shown) wherein anouter annular surface along the runner includes a plurality ofmulti-groove structures separately disposed thereon whereby the numberof grooves within adjacent multi-groove structures vary, each grooveincludes at least two steps, and each multi-groove structurecommunicates with both seal rings in accordance with an embodiment ofthe invention.

FIG. 14 is a partial cross section view illustrating an annular sealassembly including a pair of annular seal rings separated by a centerring within a seal housing disposed about a rotatable runner attached toa shaft (cross section of annular seal assembly below runner and shaftnot shown) wherein an outer annular surface along the runner includes aplurality of bifurcated multi-groove structures separately disposedthereon whereby each groove includes at least two steps, eachmulti-groove structure communicates with both seal rings, and aplurality of through holes are disposed along the rotatable runner inaccordance with an embodiment of the invention.

FIG. 15 is a cross section view illustrating the annular seal housing,the center ring, and the rotatable runner with through holes wherein theholes communicate a gas through the rotatable runner and onto the outerannular surface of the rotatable runner so that the gas enters thestepped grooves along the rotatable runner for redirection onto theinner annular surface of a first annular seal ring and a second annularseal ring in accordance with an embodiment of the invention.

FIG. 16 is a cross section view illustrating a stepped groove with anexemplary profile whereby the depth of each adjoining step decreases inthe direction opposite to rotation in accordance with an embodiment ofthe invention.

FIG. 17 is a cross section view of a rotatable runner illustrating analternate stepped groove whereby the depth of at least one adjoiningstep decreases in the direction opposite to rotation and the depth of atleast one adjoining step increases in the direction opposite to rotationin accordance with an embodiment of the invention.

FIG. 18 is a cross section view illustrating dimensions along arotatable runner and a stepped groove for calculating the distance ratio(R) based on the adjusted radial distance (r−h) over the runner radius(r_(r)) whereby the upper distance ratio (R_(U)) corresponds to theshallowest step ((r−h_(min))/r_(r)) and the lower distance ratio (R_(L))corresponds to the deepest step ((r−h_(max))/r_(r)).

FIG. 19a is an enlarged view illustrating the length (L) of a groovestructure with stepped grooves aligned diagonal to the direction ofrotation in accordance with an embodiment of the invention.

FIG. 19b is an enlarged view illustrating the length (L) of a groovestructure with stepped grooves aligned along the direction of rotationin accordance with an embodiment of the invention.

FIG. 20a is a circumferential side view illustrating a rotatable runnerwith a groove structure including a feed groove communicating withgrooves whereby each groove further includes side shoulders and baseshoulders which intersect and the side shoulders arranged in an opposedarrangement in accordance with an embodiment of the invention.

FIG. 20b is a cross section view illustrating a rotatable runner with agroove structure including a feed groove communicating with grooveswhereby each groove further includes side shoulders and base shoulderswhich intersect and the side shoulders arranged in an opposedarrangement in accordance with an embodiment of the invention.

FIG. 21a is a circumferential side view illustrating a rotatable runnerwith a groove structure including a feed groove communicating withgrooves whereby each groove further includes side shoulders and baseshoulders which are offset and the side shoulders arranged in an opposedarrangement in accordance with an embodiment of the invention.

FIG. 21b is a cross section view illustrating a rotatable runner with agroove structure including a feed groove communicating with grooveswhereby each groove further includes side shoulders and base shoulderswhich are offset and the side shoulders arranged in an opposedarrangement in accordance with an embodiment of the invention.

FIG. 22 is a circumferential side view illustrating a rotatable runnerwith a groove structure including a feed groove communicating withgrooves whereby each groove further includes side shoulders and baseshoulders which are offset and the side shoulders are arranged in anoffset arrangement in accordance with an embodiment of the invention.

FIG. 23 is a circumferential side view illustrating a rotatable runnerwith a groove structure including a feed groove communicating withgrooves whereby each groove further includes side shoulders and baseshoulders wherein one side shoulder intersects a base shoulder and otherside shoulders are arranged in an offset arrangement with respect to theintersecting side shoulder in accordance with an embodiment of theinvention.

FIG. 24 is a circumferential side view illustrating a rotatable runnerwith a groove structure including a feed groove communicating withgrooves whereby each groove further includes side shoulders and baseshoulders wherein a pair of side shoulders are disposed about a baseshoulder and the side shoulders are arranged in an offset arrangement inaccordance with an embodiment of the invention.

FIG. 25a is a circumferential side view illustrating a rotatable runnerwith a groove structure including a feed groove communicating withgrooves whereby each groove further includes side shoulders disposedalong parallel side walls and base shoulders disposed between taperedbase walls which intersect and the side shoulders arranged in an opposedarrangement in accordance with an embodiment of the invention.

FIG. 25b is a cross section view illustrating a rotatable runner with agroove structure including a feed groove communicating with grooveswhereby each groove further includes side shoulders disposed alongparallel side walls and base shoulders disposed between tapered basewalls which intersect and the side shoulders arranged in an opposedarrangement in accordance with an embodiment of the invention.

FIG. 26a is a circumferential side view illustrating a rotatable runnerwith a groove structure including a feed groove communicating withgrooves whereby each groove further includes side shoulders disposedalong tapered side walls and base shoulders disposed between parallelbase walls in accordance with an embodiment of the invention.

FIG. 26b is a cross section view illustrating a rotatable runner with agroove structure including a feed groove communicating with grooveswhereby each groove further includes side shoulders disposed alongtapered side walls and base shoulders disposed between parallel basewalls in accordance with an embodiment of the invention.

FIG. 27a is a circumferential side view illustrating a rotatable runnerwith a groove structure including a feed groove communicating withgrooves whereby each groove further includes side shoulders disposedalong tapered side walls and base shoulders disposed between taperedbase walls in accordance with an embodiment of the invention.

FIG. 27b is a cross section view illustrating a rotatable runner with agroove structure including a feed groove communicating with grooveswhereby each groove further includes side shoulders disposed alongtapered side walls and base shoulders disposed between tapered basewalls in accordance with an embodiment of the invention.

FIG. 28a is a cross section view in the downstream directionillustrating a rotatable runner with a base shoulder within a groovewhen the base shoulder does not intersect a side shoulder in accordancewith an embodiment of the invention.

FIG. 28b is a cross section view in the downstream directionillustrating a rotatable runner with a pair of side shoulders arrangedin an opposed arrangement within a groove when the side shoulders do notintersect a base shoulder in accordance with an embodiment of theinvention.

FIG. 28c is a cross section view in the downstream directionillustrating a rotatable runner with intersecting base shoulder and sideshoulders in accordance with an embodiment of the invention.

FIG. 28d is a cross section view in the downstream directionillustrating a rotatable runner with a side shoulder arranged at a leftside within a groove when the side shoulder is not arranged in anopposed arrangement with another side shoulder and the side shoulderdoes not intersect a base shoulder in accordance with an embodiment ofthe invention.

FIG. 28e is a cross section view in the downstream directionillustrating a rotatable runner with a side shoulder arranged at a rightside within a groove when the side shoulder is not arranged in anopposed arrangement with another side shoulder and the side shoulderdoes not intersect a base shoulder in accordance with an embodiment ofthe invention.

FIG. 28f is a cross section view in the downstream directionillustrating a rotatable runner with a side shoulder arranged at a leftside within a groove when the side shoulder is not arranged in anopposed arrangement with another side shoulder and the side shoulderintersects a base shoulder in accordance with an embodiment of theinvention.

FIG. 28g is a cross section view in the downstream directionillustrating a rotatable runner with a side shoulder arranged at a rightside within a groove when the side shoulder is not arranged in anopposed arrangement with another side shoulder and the side shoulderintersects a base shoulder in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to several embodiments of theinvention that are illustrated in the accompanying drawings. Whereverpossible, same or similar reference numerals are used in the drawingsand the description to refer to the same or like parts. The drawings arein simplified form and are not to precise scale.

While features of various embodiments are separately describedthroughout this document, it is understood that two or more suchfeatures are combinable to form other embodiments.

Referring now to FIG. 1, a seal assembly 1 is shown with an annular sealhousing 2, a first annular seal ring 3, and a second annular seal ring4, each disposed so as to be circumferentially arranged about arotatable runner 15 (not shown). Components are composed of materialsunderstood in the art. The rotatable runner 15 (see FIG. 2) is anelement known within the art attached to a rotatable shaft. Therotatable runner 15 is rotatable within a turbine engine via the shaft.A seal is formed along the rotatable runner 15 by each annular seal ring3, 4. The annular seal housing 2, annular seal rings 3, 4, and rotatablerunner 15 are aligned along and disposed about a centerline 14, oftencoinciding with a rotational axis within a turbine engine. The annularseal housing 2 is attached to components comprising the housingstructure 51 (generally shown) of a turbine engine fixing the annularseal housing 2 thereto. The housing structure 51 is stationary andtherefore non-rotating. The housing structure 51, seal assembly 1, andthe rotatable runner 15 generally define at least a first compartment 5and a second compartment 6. The configuration of the housing structure51 is design dependent; however, it is understood for purposes of thepresent invention that the housing structure 51 cooperates with the sealassembly 1 and rotatable runner 15 to define two separate compartmentswhereby a gas resides at a low pressure within one such compartment 5and a lubricant resides at low pressure within another compartment 6.

The annular seal housing 2 generally defines a pocket within which theannular seal rings 3, 4 reside. The annular seal housing 2 has aU-shaped cross-section opening inward toward the centerline 14. One endof the annular seal housing 2 could include an insert 7 and a retainingring 8 which allow for assembly/disassembly of the annular seal rings 3,4 onto the annular seal housing 2. The annular seal rings 3, 4 could befixed to the annular seal housing 2 via means known within the art tolimit or to prevent relative rotational motion between the annular sealrings 3, 4 and the annular seal housing 2. In one non-limiting example,a pair of anti-rotation pins 52 is secured to the annular seal housing 2to separately engage a pocket 53 along each of the first and secondannular seal rings 3, 4. Interaction between the anti-rotation pin 52and the pocket 53 functions as a positive stop to restrict rotation ofeach of the first and second annular seal rings 3, 4 with respect to theannular seal housing 2.

The first and second annular seal rings 3, 4 are ring-shaped elements.Each annular seal ring 3, 4 could be composed of at least two arcuatesegments which form a generally circular-shaped ring when assembledabout a rotatable runner 15. The segments of the first and secondannular seal rings 3, 4 allow for radial expansion and contraction bythe respective annular seal rings 3, 4 about a rotatable runner 15. Eachannular seal ring 3, 4, is generally biased toward a rotatable runner 15via a compressive force applied by a garter spring 10, 11. The garterspring 10, 11 could contact the outer circumference of the respectiveannular seal ring 3, 4 and apply a compressive force inward toward therotatable runner 15.

A plurality of springs 12 could be separately positioned between theannular seal rings 3, 4. The springs 12 could be evenly spaced about thecircumference of the annular seal rings 3, 4 so as to exert a generallyuniform separation force onto the seal rings 3, 4. The springs 12 couldbe a coil-type device which generally resists compression. Each spring12 could be attached or fixed to one annular seal ring 3, 4. Forexample, one end of each spring 12 could be partially recessed within apocket 54 along at least one annular seal ring 3, 4. Each spring 12should be sufficiently long so as to at least partially compress whenassembled between the annular seal rings 3, 4. This arrangement ensuresthat each spring 12 exerts a force onto the annular seal rings 3, 4causing the annular seal rings 3, 4 to separate, thereby pressing theannular seal rings 3, 4 onto opposite sides of the annular seal housing2. The separation force exerted by the compression spring 12 ensures agap 13 between the annular seal rings 3, 4.

At least one inlet 9 is disposed along an outer wall of the annular sealhousing 2. The inlet(s) 9 is/are positioned so as to at least partiallyoverlay the gap 13 between the annular seal rings 3, 4. Two or moreinlets 9 could be uniformly positioned about the circumference of theannular seal housing 2. Each inlet 9 is a pathway through which a gas iscommunicated into and through the gap 13 between the annular seal rings3, 4.

Although various embodiments are described including a gap 13, it isunderstood that the gap 13 as described in FIG. 1 is an optional featureand that such embodiments could include a center ring 25 with optionalgaps or optional holes 31 as shown in FIG. 4.

Referring now to FIG. 2, a seal assembly 1 is shown in cross-sectionalform disposed about a rotatable runner 15, the latter illustrated inside-view form. The rotatable runner 15 includes a plurality of groovestructures 17. The groove structures 17 are arranged circumferentiallyalong the outer annular surface 16 of the rotatable runner 15immediately adjacent to the seal assembly 1. The groove structures 17are positioned so as to communicate a gas onto the annular seal rings 3,4 as the rotatable runner 15 rotates with respect to the seal assembly1. In some embodiments, it might be advantageous for adjacent groovesstructures 17 to partially overlap as represented in FIG. 2. In otherembodiments, adjacent groove structures 17 could be arranged in anend-to-end configuration or with a separation between the end of onegroove structure 17 and the start of the next groove structure 17.

Each groove structure 17 further includes a pair of diagonal grooves 19disposed about a central axis 44 circumferentially along the outerannular surface 16 of the rotatable runner 15. The diagonal grooves 19could be aligned symmetrically or non-symmetrically about the centralaxis 44. Each diagonal groove 19 is a channel, depression, flute, or thelike disposed along the outer annular surface 16. Although the diagonalgrooves 19 are represented as linear elements, it is understood thatother designs are possible including multi-linear and non-linearconfigurations. The central axis 44 could align with the gap 13 betweenthe first and second annular seal rings 3, 4 or reside adjacent to thefirst and second annular seal rings 3, 4 to allow communication of a gasonto the groove structure 17 over the translational range of therotatable runner 15. The diagonal grooves 19 are oriented so that thetop of the left side extends toward the right and the top of the rightside extends toward the left. The inward oriented ends of the diagonalgrooves 19 intersect along or near the central axis 44 to form an apex18. The apex 18 is further oriented toward the rotational direction ofthe rotatable runner 15 so that the diagonal grooves 19 expand outwardopposite of the rotational direction. The dimensions and angularorientation of the diagonal grooves 19 and the apex 18 are designdependent and based in part on the translational range of the rotatablerunner 15, the widths of the annular seal rings 3, 4 and gap 13, theextent of overlap or non-overlap between adjacent groove structures 17,the pressure required to adequately seal the interface between therotatable runner 15 and the annular seal rings 3, 4, and/or other designfactors.

Each diagonal groove 19 further includes at least two optional steps 62a-62 d. Although four steps 62 a-62 d are illustrated along eachdiagonal groove 19 in FIG. 2, it is understood that two or more suchsteps 62 a-62 d may reside along each diagonal groove 19. Each step 62a-62 d corresponds to a change in the local depth of the diagonal groove19 relative to the outer annular surface 16. For example, if a diagonalgroove 19 includes two steps 62 a, 62 b, then one step 62 a would have afirst depth and another step 62 b would have a second depth. The depthsdiffer so that one depth is deeper and another depth is shallower. Inpreferred arrangements, the steps 62 a-62 d are arranged so that thechange in local depth from one step to another step results in astepwise variation along the length of each diagonal groove 19.

When the diagonal grooves 19 intersect at an apex 18 or the like, thefirst step 62 a may be located at the apex 18 and immediately adjacentto and communicable with the next step 62 b along each diagonal groove19 extending from the apex 18, as illustrated in FIG. 2. In otherembodiments, two or more steps may reside within the apex 18 and atleast one step along each diagonal groove 19. In yet other embodiments,one step 62 a may reside along the apex 18 and a portion of one or morediagonal grooves 19 and the remaining step(s) 62 b reside(s) exclusivelyalong each diagonal groove 19. Regardless of the exact arrangement, thesteps 62 a-62 d are arranged consecutively to effect a stepwisevariation of the depth along the length of each groove structure 17.

In the various embodiments, the gas could originate from a combustion ormechanical source within a turbine engine. In some embodiments, the gascould be a gas heated by combustion events within an engine andcommunicated to the inlet(s) 9 from a compartment adjacent to the firstand second compartments 5, 6. In other embodiments, the gas could beeither a hot or cold gas pressurized and communicated to the outlet(s) 9via a fan or a pump.

Referring again to FIG. 2, a gas enters the inlet(s) 9 and is directedinward across the gap 13 between the first and second annular seal rings3, 4. After exiting the gap 13, the gas impinges the outer annularsurface 16 of the rotatable runner 15, preferably at or near the apex 18or inlet end 45. The gas enters the apex 18 or inlet end 45 and isbifurcated by the groove structure 17 so that a first portion isdirected into the left-side diagonal groove 19 and a second portion isdirected into the right-side diagonal groove 19. The quantity and/orrate of gas communicated onto each of the annular seal rings 3, 4 may bethe same or different. The gas traverses the respective diagonal grooves19 and is redirected outward from the rotatable runner 15 at the outletend 46 of each diagonal groove 19. The gas exits the left-side diagonalgroove 19 and impinges the first annular seal ring 3 forming a thin-filmlayer 20 between the first annular seal ring 3 and rotatable runner 15,thereby separating the first annular seal ring 3 from the rotatablerunner 15. The gas exits the right-side diagonal groove 19 and impingesthe second annular seal ring 4 forming a thin-film layer 20 between thesecond annular seal ring 4 and rotatable runner 15, thereby separatingthe second annular seal ring 4 from the rotatable runner 15.

Referring now to FIG. 3, a seal assembly 1 is shown in cross-sectionalform disposed about a rotatable runner 15, the latter illustrated inside-view form, between a pair of compartments 5, 6. The rotatablerunner 15 includes a plurality of groove structures 17. The groovestructures 17 are arranged circumferentially along the outer annularsurface 16 of the rotatable runner 15 immediately adjacent to the sealassembly 1. The groove structures 17 are positioned so as to communicatea gas onto the annular seal rings 3, 4 as the rotatable runner 15rotates with respect to the seal assembly 1. In some embodiments, itmight be advantageous for adjacent grooves structures 17 to partiallyoverlap as represented in FIG. 3. In other embodiments, adjacent groovestructures 17 could be arranged in an end-to-end configuration or with aseparation between the end of one groove structure 17 and the start ofthe next groove structure 17.

Each groove structure 17 further includes a pair of diagonal grooves 19disposed about a central axis 44 circumferentially along an outerannular surface 16 of the rotatable runner 15. The diagonal grooves 19could be aligned symmetrically or non-symmetrically about the centralaxis 44. Each diagonal groove 19 is a channel, depression, flute, or thelike disposed along the outer annular surface 16. Although the diagonalgrooves 19 are represented as linear elements, it is understood thatother designs are possible including multi-linear and non-linearconfigurations. The central axis 44 could align with the gap 13 betweenfirst and second annular seal rings 3, 4 or reside adjacent to the firstand second annular seal rings 3, 4 to allow communication of a gas ontothe groove structure 17 over the translational range of the rotatablerunner 15. The diagonal grooves 19 are oriented so that the top of theleft-side extends toward the right and the top of the right-side extendstoward the left. The inward oriented ends of the diagonal grooves 19intersect an annular groove 39 along the central axis 44. The annulargroove 39 is a channel, depression, flute, or the like circumferentiallyalong the outer annular surface 16 of the rotatable runner 15. Althoughthe annular groove 39 is represented as linear elements, it isunderstood that other designs are possible including multi-linear andnon-linear configurations. The intersection point between the diagonalgrooves 19 and the annular groove 39 is oriented toward the rotationaldirection of the rotatable runner 15 so that the diagonal grooves 19expand outward opposite of the rotational direction. The dimensions andangular orientation of the diagonal grooves 19 and annular groove 39 aredesign dependent and based in part on the translational range of therotatable runner 15, the width of the annular seal rings 3, 4 and gap13, the extent of overlap or non-overlap between adjacent groovestructures 17, the pressure required to adequately seal the interfacebetween the rotatable runner 15 and annular seal rings 3, 4, and/orother design factors.

Each diagonal groove 19 further includes at least two optional steps 62a-62 d. Although four steps 62 a-62 d are illustrated along eachdiagonal groove 19 in FIG. 3, it is understood that two or more suchsteps 62 a-62 d may reside along each diagonal groove 19. Each step 62a-62 d corresponds to a change in the local depth of the diagonal groove19 relative to the outer annular surface 16. For example, if a diagonalgroove 19 includes two steps 62 a, 62 b, then one step 62 a would have afirst depth and another step 62 b would have a second depth. The depthsdiffer so that one depth is deeper and another depth is shallower. Inpreferred arrangements, the steps 62 a-62 d are arranged so that thechange in local depth from one step to another step results in astepwise variation along the length of each diagonal groove 19.

When the diagonal grooves 19 intersect an annular groove 39 or the like,the first step 62 a is immediately adjacent to and communicable with theannular groove 39 as illustrated in FIG. 3. The depth of the first step62 a may be deeper than, shallower than, or the same as the depth of theannular groove 39. Regardless of the exact arrangement, the steps 62a-62 d are arranged consecutively to effect a stepwise variation of thedepth along the length of each groove structure 17.

Referring again to FIG. 3, a gas enters the inlet(s) 9 and is directedinward across the gap 13 between the first and second annular seal rings3, 4. After exiting the gap 13, the gas impinges the outer annularsurface 16 of the rotatable runner 15, preferably at or near the annulargroove 39. The gas enters the annular groove 39 and is bifurcated by thegroove structure 17 so that a first portion is directed into the inletend 45 of the left-side diagonal groove 19 and a second portion isdirected into the inlet end 45 of the right-side diagonal groove 19. Thequantity and/or rate of gas communicated onto each of the annular sealrings 3, 4 may be the same or different. The continuity of the annulargroove 39 allows for uninterrupted communication of the gas into thediagonal grooves 19. The gas traverses the respective diagonal grooves19 and is redirected outward from the rotatable runner 15 at the outletend 46 of each diagonal groove 19. The gas exits the left-side diagonalgroove 19 and impinges the first annular seal ring 3 forming a thin-filmlayer 20 between the first annular seal ring 3 and rotatable runner 15,thereby separating the first annular seal ring 3 from the rotatablerunner 15. The gas exits the right-side diagonal groove 19 and impingesthe second annular seal ring 4 forming a thin-film layer 20 between thesecond annular seal ring 4 and rotatable runner 15, thereby separatingthe second annular seal ring 4 from the rotatable runner 15.

Referring now to FIG. 4, a seal assembly 21 is shown with an annularseal housing 22, a first annular seal ring 23, a second annular sealring 24, and a center ring 25, each disposed so as to becircumferentially arranged about a rotatable runner 35 (see FIG. 5).Components are composed of materials understood in the art. Therotatable runner 35 is an element known within the art attached to arotatable shaft (not shown). The rotatable runner 35 is rotatable withinthe turbine engine via the shaft. A seal is formed along the rotatablerunner 35 by each annular seal ring 23, 24. The annular seal housing 22,annular seal rings 23, 24, center ring 25, and rotatable runner 35 arealigned along and disposed about a centerline 34, often coinciding witha rotational axis along a turbine engine. The annular seal housing 22 isattached to components comprising the housing structure 51 (generallyshown) of a turbine engine fixing the annular seal housing 22 thereto.The housing structure 51 is stationary and therefore non-rotating. Thehousing structure 51, seal assembly 21, and the rotatable runner 35generally define at least a first compartment 5 and a second compartment6. The configuration of the housing structure 51 is design dependent;however, it is understood for purposes of the present invention that thehousing structure 51 cooperates with the seal assembly 1 and rotatablerunner 35 to define two separate compartments whereby a gas resides at alow pressure within one such compartment 5 and a lubricant resides atlow pressure within another compartment 6.

The annular seal housing 22 generally defines a pocket within which theannular seal rings 23, 24 and center ring 25 reside. The annular sealhousing 22 could have a U-shaped cross-section opening inward toward thecenterline 34. One end of the annular seal housing 22 could include aninsert 27 and a retaining ring 28 which allow for assembly/disassemblyof the annular seal rings 23, 24 and center ring 25 onto the annularseal housing 22. The annular seal rings 23, 24 could be fixed to theannular seal housing 22 via means known within the art to limit or toprevent relative rotational motion between the annular seal rings 23, 24and the annular seal housing 22. In one non-limiting example, a pair ofanti-rotation pins 52 is secured to the annular seal housing 22 toseparately engage a pocket 53 along each of the first and second annularseal rings 23, 24. Interaction between anti-rotation pin 52 and pocket53 functions as a positive stop to restrict rotation of each of thefirst and second annular seal rings 23, 24 with respect to the annularseal housing 22.

The first and second annular seal rings 23, 24 are ring-shaped elements.Each annular seal ring 23, 24 could comprise at least two arcuatesegments which form a generally circular-shaped ring when assembledabout a rotatable runner 35. The segmented construction of the first andsecond annular seal rings 3, 4 allows for radial expansion andcontraction by the respective annular seal rings 23, 24 about arotatable runner 35. Each annular seal ring 23, 24, is generally biasedtoward a rotatable runner 35 via a compressive force applied by a garterspring 29, 30. The garter spring 29, 30 could contact the outercircumference of the respective annular seal ring 23, 24 and apply thecompressive force inward toward the rotatable runner 35.

The center ring 25 is interposed between the first and second annularseal rings 23, 24 within the annular seal housing 22. A plurality offirst springs 32 are interposed between the first annular seal ring 23and the center ring 25. A plurality of second springs 33 are interposedbetween the second annular seal ring 24 and the center ring 25. Thefirst and second springs 32, 33 could be evenly spaced about thecircumference of the respective annular seal rings 23, 24 so as to exerta generally uniform separation force onto each annular seal ring 23, 24with respect to the center ring 25. The first and second springs 32, 33could be a coil-type device which generally resists compression. Eachspring 32, 33 could be attached or fixed to the respective annular sealring 23, 24. For example, one end of each first and second spring 32, 33could be partially recessed within a pocket 54 along the respectiveannular seal ring 23, 24. First and second springs 32, 33 should besufficiently long so as to at least partially compress when assembledbetween the respective annular seal rings 23, 24 and center ring 25.First and second springs 32, 33 should exert a force onto the annularseal rings 23, 24 causing the annular seal rings 23, 24 to separate fromthe center ring 25, thereby pressing the annular seal rings 23, 24 ontoopposite sides of the annular seal housing 22 with the center ring 25substantially centered between the annular seal rings 23, 24. Theseparation force exerted by the compression springs 32, 33 could form anoptional gap (not shown) between the center ring 25 and each annularseal ring 23, 24.

At least one inlet 26 is disposed along an outer wall of the annularseal housing 22. The inlet(s) 26 is/are positioned so as to at leastpartially overlay the center ring 25 between the annular seal rings 23,24. Two or more inlets 26 could be uniformly positioned about thecircumference of the annular seal housing 22. Each inlet 26 is a pathwaythrough which a gas is communicated between the annular seal rings 23,24.

In some embodiments, the center ring 25 could include a plurality ofholes 31 traversing the radial dimension of the center ring 25. Theholes 31 could be evenly spaced about the circumference of the centerring 25 and positioned so as to at least partially overlay the inlet(s)26.

Although various embodiments are described including a center ring 25,it is understood that the center ring 25 is an optional feature and thatsuch embodiments could include the gap 13 arrangement shown in FIG. 1.

Referring now to FIG. 5, a seal assembly 21 is shown in cross-sectionalform disposed about a rotatable runner 35, the latter illustrated inside-view form, between a pair of compartments 5, 6. The rotatablerunner 35 includes a plurality of groove structures 37. The groovestructures 37 are arranged circumferentially along the outer annularsurface 36 of the rotatable runner 35 immediately adjacent to the sealassembly 21. The groove structures 37 are positioned so as tocommunicate a gas onto the annular seal rings 23, 24 as the rotatablerunner 35 rotates with respect to the seal assembly 21. In someembodiments, it might be advantageous for adjacent grooves structures 37to partially overlap as represented in FIG. 5. In other embodiments,adjacent groove structures 37 could be arranged in an end-to-endconfiguration or with a separation between the end of one groovestructure 37 and the start of the next groove structure 37.

Each groove structure 37 further includes a pair of diagonal grooves 38disposed about a central axis 44 circumferentially along an outerannular surface 36 of the rotatable runner 35. The diagonal grooves 38could be aligned symmetrically or non-symmetrically about the centralaxis 44. Each diagonal groove 38 is a channel, depression, flute, or thelike disposed along the outer annular surface 36. Although the diagonalgrooves 38 are represented as linear elements, it is understood thatother designs are possible including multi-linear and non-linearconfigurations. The central axis 44 could align with the center ring 25between first and second annular seal rings 23, 24 or reside adjacent tothe first and second annular seal rings 23, 24 to allow communication ofa gas onto the groove structures 37 over the translational range of therotatable runner 35. The diagonal grooves 38 are oriented so that thetop of the left-side diagonal groove 38 extends toward the right and thetop of the right-side diagonal groove 38 extends toward the left. Theinward oriented ends of the diagonal grooves 38 intersect along or nearthe central axis 44 to form an apex 40. The apex 40 is further orientedtoward the rotational direction of the rotatable runner 35 so that thediagonal grooves 38 expand outward opposite of the rotational direction.The dimensions and angular orientation of the diagonal grooves 38 andthe apex 40 are design dependent and based in part on the translationalrange of the rotatable runner 35, the widths of the annular seal rings23, 24, center ring 25 and optional hole 31, the extent of overlap ornon-overlap between adjacent groove structures 37, the pressure requiredto adequately seal the interface between the rotatable runner 35 andannular seal rings 23, 24, and/or other design factors.

Each diagonal groove 38 further includes at least two optional steps 62a-62 d. Although four steps 62 a-62 d are illustrated along eachdiagonal groove 38 in FIG. 5, it is understood that two or more suchsteps 62 a-62 d may reside along each diagonal groove 38. Each step 62a-62 d corresponds to a change in the local depth of the diagonal groove38 relative to the outer annular surface 36. For example, if a diagonalgroove 38 includes two steps 62 a, 62 b, then one step 62 a would have afirst depth and another step 62 b would have a second depth. The depthsdiffer so that one depth is deeper and another depth is shallower. Inpreferred arrangements, the steps 62 a-62 d are arranged so that thechange in local depth from one step to another step results in astepwise variation along the length of each diagonal groove 38.

When the diagonal grooves 38 intersect at an apex 40 or the like, thefirst step 62 a may be located at the apex 40 and immediately adjacentto and communicable with the next step 62 b along each diagonal groove38 extending from the apex 40, as illustrated in FIG. 5. In otherembodiments, two or more steps may reside within the apex 40 and atleast one step along each diagonal groove 38. In yet other embodiments,one step 62 a may reside along the apex 40 and a portion of one or morediagonal grooves 38 and the remaining step(s) 62 b reside(s) exclusivelyalong each diagonal groove 38. Regardless of the exact arrangement, thesteps 62 a-62 d are arranged consecutively to effect a stepwisevariation of the depth along the length of each groove structure 37.

Referring again to FIG. 5, a gas enters the inlet(s) 26 and is directedinward onto the center ring 25. The gas flows around the center ring 25traversing the gaps between the center ring 25 and the first and secondannular seal rings 23, 24 when the center ring 25 does not include theoptional holes 31. The gas traverses the holes 31 when the center ring25 includes the optional holes 31. Next, the gas impinges the outerannular surface 36 of the rotatable runner 35, preferably at or near theapex 40 or inlet end 45. The gas enters the apex 40 or inlet end 45 andis bifurcated by the groove structure 37 so that a first portion isdirected into the left-side diagonal groove 38 and a second portion isdirected into the right-side diagonal groove 38. The quantity and/orrate of gas communicated onto each of the annular seal rings 23, 24 maybe the same or different. The gas traverses the respective diagonalgrooves 38 and is redirected outward from the rotatable runner 35 at theoutlet end 46 of each diagonal groove 38. The gas exits the left-sidediagonal groove 38 and impinges the first annular seal ring 23 forming athin-film layer 20 between the first annular seal ring 23 and rotatablerunner 35, thereby separating the first annular seal ring 23 from therotatable runner 35. The gas exits the right-side diagonal groove 38 andimpinges the second annular seal ring 24 forming a thin-film layer 20between the second annular seal ring 24 and rotatable runner 35, therebyseparating the second annular seal ring 24 from the rotatable runner 35.

Referring now to FIG. 6, a seal assembly 21 is shown in cross-sectionalform disposed about a rotatable runner 35, the latter illustrated inside-view form, between a pair of compartments 5, 6. The rotatablerunner 35 includes a plurality of groove structures 37. The groovestructures 37 are arranged circumferentially along the outer annularsurface 36 of the rotatable runner 35 immediately adjacent to the sealassembly 21. The groove structures 37 are positioned so as tocommunicate a gas onto the annular seal rings 23, 24 as the rotatablerunner 35 rotates with respect to the seal assembly 21. In someembodiments, it might be advantageous for adjacent grooves structures 37to partially overlap as represented in FIG. 6. In other embodiments,adjacent groove structures 37 could be arranged in an end-to-endconfiguration or with a separation between the end of one groovestructure 37 and the start of the next groove structure 37.

Each groove structure 37 further includes a pair of diagonal grooves 38disposed about a central axis 44 circumferentially along an outerannular surface 36 of the rotatable runner 35. The diagonal grooves 38could be aligned symmetrically or non-symmetrically about the centralaxis 44. Each diagonal groove 38 is a channel, depression, flute, or thelike disposed along the outer annular surface 36. Although the diagonalgrooves 38 are represented as linear elements, it is understood thatother designs are possible including multi-linear and non-linearconfigurations. The central axis 44 could align with the center ring 25between first and second annular seal rings 23, 24 or reside adjacent tothe first and second annular seal rings 23, 24 to allow communication ofa gas onto the groove structures 37 over the translational range of therotatable runner 35. The diagonal grooves 38 are oriented so that thetop of the left-side diagonal groove 38 extends toward the right and thetop of the right-side diagonal groove 38 extends toward the left. Theinward oriented ends of the diagonal grooves 38 are separately disposedabout the central axis 44 so that the diagonal grooves 38 expand outwardopposite of the rotational direction. The dimensions and angularorientation of the diagonal grooves 38 are design dependent and based inpart on the translational range of the rotatable runner 35, the widthsof the annular seal rings 23, 24, center ring 25 and optional hole 31,the extent of overlap or non-overlap between adjacent groove structures37, the pressure required to adequately seal the interface between therotatable runner 35 and annular seal rings 23, 24, and/or other designfactors.

Each diagonal groove 38 further includes at least two optional steps 62a-62 d. Although four steps 62 a-62 d are illustrated along eachdiagonal groove 38 in FIG. 6, it is understood that two or more suchsteps 62 a-62 d may reside along each diagonal groove 38. Each step 62a-62 d corresponds to a change in the local depth of the diagonal groove38 relative to the outer annular surface 36. For example, if a diagonalgroove 38 includes two steps 62 a, 62 b, then one step 62 a would have afirst depth and another step 62 b would have a second depth. The depthsdiffer so that one depth is deeper and another depth is shallower. Inpreferred arrangements, the steps 62 a-62 d are arranged so that thechange in local depth from one step to another step results in astepwise variation along the length of each diagonal groove 38.Regardless of the exact arrangement, the steps 62 a-62 d are arrangedconsecutively to effect a stepwise variation of the depth along thelength of each groove structure 37.

Referring again to FIG. 6, a gas enters the inlet(s) 26 and is directedinward onto the center ring 25. The gas flows around the center ring 25traversing the gaps between the center ring 25 and the first and secondannular seal rings 23, 24 when the center ring 25 does not include theoptional holes 31. The gas traverses the holes 31 when the center ring25 includes the optional holes 31. Next, the gas impinges the outerannular surface 36 of the rotatable runner 35, preferably at or nearinlet ends 45. The gas is bifurcated by the groove structure 37 at theinlet ends 45 so that a first portion is directed into the left-sidediagonal groove 38 and a second portion is directed into the right-sidediagonal groove 38. The quantity and/or rate of gas communicated ontoeach of the annular seal rings 23, 24 may be the same or different. Thegas traverses the respective diagonal grooves 38 and is redirectedoutward from the rotatable runner 35 at the outlet end 46 of eachdiagonal groove 38. The gas exits the left-side diagonal groove 38 andimpinges the first annular seal ring 23 forming a thin-film layer 20between the first annular seal ring 23 and rotatable runner 35, therebyseparating the first annular seal ring 23 from the rotatable runner 35.The gas exits the right-side diagonal groove 38 and impinges the secondannular seal ring 24 forming a thin-film layer 20 between the secondannular seal ring 24 and rotatable runner 35, thereby separating thesecond annular seal ring 24 from the rotatable runner 35.

Referring now to FIG. 7, a seal assembly 21 is shown in cross-sectionalform disposed about a rotatable runner 35, the latter illustrated inside-view form, between a pair of compartments 5, 6. The rotatablerunner 35 includes a plurality of groove structures 41. The groovestructures 41 are arranged circumferentially along the outer annularsurface 36 of the rotatable runner 35 immediately adjacent to the sealassembly 21. The groove structures 41 are positioned so as tocommunicate a gas onto the annular seal rings 23, 24 as the rotatablerunner 35 rotates with respect to the seal assembly 21. In someembodiments, it might be advantageous for adjacent grooves structures 41to partially overlap. In other embodiments, adjacent groove structures41 could be arranged in an end-to-end configuration or with a separationbetween the end of one groove structure 41 and the start of the nextgroove structure 41, the latter represented in FIG. 7.

Each groove structure 41 further includes a plurality of diagonalgrooves 43 disposed about a central axis 44 circumferentially along anouter annular surface 36 of the rotatable runner 35. The diagonalgrooves 43 could be aligned symmetrically or non-symmetrically about thecentral axis 44. Each diagonal groove 43 is a channel, depression,flute, or the like disposed along the outer annular surface 36. Althoughthe diagonal grooves 43 are represented as linear elements, it isunderstood that other designs are possible including multi-linear andnon-linear configurations. The central axis 44 could align with thecenter ring 25 between first and second annular seal rings 23, 24 orreside adjacent to the first and second annular seal rings 23, 24 toallow communication of a gas onto the groove structures 41 over thetranslational range of the rotatable runner 35. The diagonal grooves 43are oriented so that the top of each left-side diagonal groove 43extends toward the right and the top of each right-side diagonal groove43 extends toward the left. The inward oriented ends of the diagonalgrooves 43 are separately disposed about the central axis 44 so that thediagonal grooves 43 expand outward opposite of the rotational direction.

At least two diagonal grooves 43 are disposed along each side of thecentral axis 44. In some embodiments, the diagonal grooves 43 could besubstantially parallel to other diagonal grooves 43 along the same sideof the central axis 44 as represented by the set of three diagonalgrooves 43 along each side of the central axis 44 in FIG. 7. In otherembodiments, the diagonal grooves 43 could be oriented at two or moreangles with respect to the rotational direction and/or central axis 44whereby the diagonal grooves 43 along the same side of the central axis44 are non-parallel. It is also possible in some embodiments for theinlet ends 45 and the outlet ends 46 to be aligned circumferentially asrepresented in FIG. 7. In yet other embodiments, the inlet ends 45 andthe outlet ends 46 could be skewed or staggered and/or the diagonalgrooves 43 have the same or different lengths.

The dimensions, angular orientation and number of the diagonal grooves43 are design dependent and based in part on the translational range ofthe rotatable runner 35, the widths of the annular seal rings 23, 24,center ring 25 and optional hole 31, the extent of overlap ornon-overlap between adjacent groove structures 41, the number of flowsfrom a groove structure 41 required to impinge each annular seal ring23, 24, the pressure required to adequately seal the interface betweenthe rotatable runner 35 and annular seal rings 23, 24, and/or otherdesign factors.

Each diagonal groove 43 further includes at least two optional steps 62a-62 d. Although four steps 62 a-62 d are illustrated along eachdiagonal groove 43 in FIG. 7, it is understood that two or more suchsteps 62 a-62 d may reside along each diagonal groove 43. Each step 62a-62 d corresponds to a change in the local depth of the diagonal groove43 relative to the outer annular surface 36. For example, if a diagonalgroove 43 includes two steps 62 a, 62 b, then one step 62 a would have afirst depth and another step 62 b would have a second depth. The depthsdiffer so that one depth is deeper and another depth is shallower. Inpreferred arrangements, the steps 62 a-62 d are arranged so that thechange in local depth from one step to another step results in astepwise variation along the length of each diagonal groove 43.Regardless of the exact arrangement, the steps 62 a-62 d are arrangedconsecutively to effect a stepwise variation of the depth along thelength of each groove structure 41.

Referring again to FIG. 7, a gas enters the inlet(s) 26 and is directedinward onto the center ring 25. The gas flows around the center ring 25traversing the gaps between the center ring 25 and the first and secondannular seal rings 23, 24 when the center ring 25 does not include theoptional holes 31. The gas traverses the holes 31 when the center ring25 includes the optional holes 31. Next, the gas impinges the outerannular surface 36 of the rotatable runner 35, preferably at or nearinlet ends 45. The gas is bifurcated by the groove structure 41 at theinlet ends 45 so that a first portion is directed into the left-sidediagonal grooves 43 and a second portion is directed into the right-sidediagonal grooves 43. The quantity and/or rate of gas communicated ontoeach of the annular seal rings 23, 24 may be the same or different. Thegas traverses the respective diagonal grooves 43 and is redirectedoutward from the rotatable runner 35 at the outlet end 46 of eachdiagonal groove 43. The gas exits at least one left-side diagonal groove43 within a groove structure 41 and impinges the first annular seal ring23 forming a thin-film layer 20 between the first annular seal ring 23and rotatable runner 35, thereby separating the first annular seal ring23 from the rotatable runner 35. The gas exits at least one right-sidediagonal groove 43 within a groove structure 41 and impinges the secondannular seal ring 24 forming a thin-film layer 20 between the secondannular seal ring 24 and rotatable runner 35, thereby separating thesecond annular seal ring 24 from the rotatable runner 35.

Referring now to FIG. 8, a seal assembly 21 is shown in cross-sectionalform disposed about a rotatable runner 35, the latter illustrated inside-view form, between a pair of compartments 5, 6. The rotatablerunner 35 includes a plurality of groove structures 41. The groovestructures 41 are arranged circumferentially along the outer annularsurface 36 of the rotatable runner 35 immediately adjacent to the sealassembly 21. The groove structures 41 are positioned so as tocommunicate a gas onto the annular seal rings 23, 24 as the rotatablerunner 35 rotates with respect to the seal assembly 21. In someembodiments, it might be advantageous for adjacent grooves structures 41to partially overlap. In other embodiments, adjacent groove structures41 could be arranged in an end-to-end configuration or with a separationbetween the end of one groove structure 41 and the start of the nextgroove structure 41, the latter represented in FIG. 8. Each groovestructure 41 further includes at least two of diagonal grooves 43disposed about a central axis 44 circumferentially along an outerannular surface 36 of the rotatable runner 35. The diagonal grooves 43could be aligned symmetrically or non-symmetrically about the centralaxis 44. Each diagonal groove 43 is a channel, depression, flute, or thelike disposed along the outer annular surface 36. Although the diagonalgrooves 43 are represented as linear elements, it is understood thatother designs are possible including multi-linear and non-linearconfigurations. The central axis 44 could align with the center ring 25between first and second annular seal rings 23, 24 or reside adjacent tothe first and second annular seal rings 23, 24 to allow communication ofa gas onto the groove structures 41 over the translational range of therotatable runner 35. The diagonal grooves 43 are oriented so that thetop of each left-side diagonal groove 43 extends toward the right andthe top of each right-side diagonal groove 43 extends toward the left.The inward oriented ends of the diagonal grooves 43 are separatelydisposed about the central axis 44 so that the diagonal grooves 43expand outward opposite of the rotational direction.

At least one diagonal groove 43 is disposed along each side of thecentral axis 44. When two or more diagonal grooves 43 are disposed alongeach side of the central axis 44, the diagonal grooves 43 could besubstantially parallel to other diagonal grooves 43 along the same sideof the central axis 44 as represented by the set of three diagonalgrooves 43 along each side of the central axis 44 in FIG. 8. In otherembodiments, the diagonal grooves 43 could be oriented at two or moreangles with respect to the rotational direction and/or central axis 44whereby the diagonal grooves 43 along the same side of the central axis44 are non-parallel. Two or more of the inlet ends 45 and the outletends 46 could be aligned circumferentially as represented in FIG. 8. Twoor more of other inlet ends 45 and outlet ends 46 could be skewed orstaggered as also represented in FIG. 8. Two or more diagonal grooves 43could have the same or different lengths as further represented in FIG.8.

Two or more diagonal grooves 43 could communicate with a feed groove 42at the inlet ends 45 of the diagonal grooves 43. The feed groove 42 is achannel, depression, flute, or the like disposed along the outer annularsurface 36. Although the feed groove 42 is represented as a linearelement, it is understood that other designs are possible includingmulti-linear and non-linear configurations. The feed groove 42 isgenerally oriented to traverse the central axis 44 so as tocommunication with diagonal grooves 43 along both sides of the groovestructure 41. The feed groove 42 could be substantially perpendicular tothe rotational direction of the rotatable runner 35 and/or the centralaxis 44 as represented in FIG. 8. In other embodiments the feed groove42 could be obliquely oriented with respect to the rotational directionand/or central axis 44. When less than all diagonal grooves 43communicate with a feed groove 42 it is possible for the diagonalgrooves 43 to intersect as described in FIGS. 2 and 5 to form asecondary groove structure 55 within the larger primary groove structure41, as represented in FIG. 8.

The dimensions, angular orientation and number of the diagonal grooves43 and feed groove 42 are design dependent and based in part on thetranslational range of the rotatable runner 35, the widths of theannular seal rings 23, 24, center ring 25 and optional hole 31, theextent of overlap or non-overlap between adjacent groove structures 41with or without secondary groove structures 55, the number of flows froma groove structure 41 required to impinge each annular seal ring 23, 24,the pressure required to adequately seal the interface between therotatable runner 35 and annular seal rings 23, 24, and/or other designfactors.

Each diagonal groove 43 further includes at least two optional steps 62a-62 d. Although three or four steps 62 a-62 d are illustrated along thediagonal grooves 43 in FIG. 8, it is understood that two or more suchsteps 62 a-62 d may reside along each diagonal groove 43. Each step 62a-62 d corresponds to a change in the local depth of the diagonal groove43 relative to the outer annular surface 36. For example, if a diagonalgroove 43 includes two steps 62 a, 62 b, then one step 62 a would have afirst depth and another step 62 b would have a second depth. The depthsdiffer so that one depth is deeper and another depth is shallower. Inpreferred arrangements, the steps 62 a-62 d are arranged so that thechange in local depth from one step to another step results in astepwise variation along the length of each diagonal groove 43.

When the diagonal grooves 43 intersect at an apex as otherwise describedherein or a feed groove 40, the first step 62 a may be located at theapex or the feed groove 40 and immediately adjacent to and communicablewith the next step 62 b along each diagonal groove 43, as illustrated inFIG. 8. In other embodiments, two or more steps may reside within theapex or the feed groove 40 and at least one step along each diagonalgroove 43. In yet other embodiments, one step 62 a may reside along theapex or the feed groove 40 and a portion of one or more diagonal grooves43 and the remaining step(s) 62 b reside(s) exclusively along eachdiagonal groove 43, as also illustrated in FIG. 8. Regardless of theexact arrangement, the steps 62 a-62 d are arranged consecutively toeffect a stepwise variation of the depth along the length of each groovestructure 41 and each secondary groove structure 55.

Referring again to FIG. 8, a gas enters the inlet(s) 26 and is directedinward onto the center ring 25. The gas flows around the center ring 25traversing the gaps between the center ring 25 and the first and secondannular seal rings 23, 24 when the center ring 25 does not include theoptional holes 31. The gas traverses the holes 31 when the center ring25 includes the optional holes 31. Next, the gas impinges the feedgroove 42 along the outer annular surface 36 of the rotatable runner 35.The gas is bifurcated along the feed groove 42 allowing the gas to enterthe inlet ends 45 so that a first portion is directed into the left-sidediagonal grooves 43 and a second portion is directed into the right-sidediagonal grooves 43. The quantity and/or rate of gas communicated ontoeach of the annular seal rings 23, 24 may be the same or different. Thegas traverses the respective diagonal grooves 43 and is redirectedoutward from the rotatable runner 35 at the outlet end 46 of eachdiagonal groove 43. The gas exits at least one left-side diagonal groove43 within a groove structure 41 and impinges the first annular seal ring23 forming a thin-film layer 20 between the first annular seal ring 23and rotatable runner 35, thereby separating the first annular seal ring23 from the rotatable runner 35. The gas exits at least one right-sidediagonal groove 43 within a groove structure 41 and impinges the secondannular seal ring 24 forming a thin-film layer 20 between the secondannular seal ring 24 and rotatable runner 35, thereby separating thesecond annular seal ring 24 from the rotatable runner 35. The flowcharacteristics of the secondary groove structure 55 are as describedfor FIGS. 2 and 5.

Referring now to FIG. 9, a seal assembly 21 is shown in cross-sectionalform disposed about a rotatable runner 35, the latter illustrated inside-view form, between a pair of compartments 5, 6. The rotatablerunner 35 includes a plurality of groove structures 41. The groovestructures 41 are arranged circumferentially along the outer annularsurface 36 of the rotatable runner 35 immediately adjacent to the sealassembly 21. The groove structures 41 are positioned so as tocommunicate a gas onto the annular seal rings 23, 24 as the rotatablerunner 35 rotates with respect to the seal assembly 21. In someembodiments, it might be advantageous for adjacent grooves structures 41to partially overlap. In other embodiments, adjacent groove structures41 could be arranged in an end-to-end configuration or with a separationbetween the end of one groove structure 41 and the start of the nextgroove structure 41, the latter represented in FIG. 9.

Each groove structure 41 further includes at least two diagonal grooves43 disposed about a central axis 44 circumferentially along an outerannular surface 36 of the rotatable runner 35. The diagonal grooves 43could be aligned symmetrically or non-symmetrically about the centralaxis 44. Each diagonal groove 43 is a channel, depression, flute, or thelike disposed along the outer annular surface 36. Although the diagonalgrooves 43 are represented as linear elements, it is understood thatother designs are possible including multi-linear and non-linearconfigurations. The central axis 44 could align with the center ring 25between first and second annular seal rings 23, 24 or reside adjacent tothe first and second annular seal rings 23, 24 to allow communication ofa gas onto the groove structures 41 over the translational range of therotatable runner 35. The diagonal grooves 43 are oriented so that thetop of each left-side diagonal groove 43 extends toward the right andthe top of each right-side diagonal groove 43 extends toward the left.The inward oriented ends of the diagonal grooves 43 are separatelydisposed about the central axis 44 so that the diagonal grooves 43expand outward opposite of the rotational direction.

At least two diagonal grooves 43 are disposed along each side of thecentral axis 44. The diagonal grooves 43 could be substantially parallelto other diagonal grooves 43 along the same side of the central axis 44as represented by the set of three diagonal grooves 43 along each sideof the central axis 44 in FIG. 9. In other embodiments, the diagonalgrooves 43 could be oriented at two or more angles with respect to therotational direction and/or central axis 44 whereby the diagonal grooves43 along the same side of the central axis 44 are non-parallel. Two ormore of the inlet ends 45 and the outlet ends 46 could be alignedcircumferentially as represented in FIG. 9. Two or more inlet ends 45and outlet ends 46 could be skewed or staggered. Two or more diagonalgroove 43 could have the same or different lengths.

Two or more diagonal grooves 43 could communicate with a first feedgroove 56 at the inlet ends 45 of the left-side diagonal grooves 43. Twoor more other diagonal grooves 43 could communicate with a second feedgroove 57 at the inlet ends 45 of the right-side diagonal grooves 43.Each first and second feed groove 56, 57 is a channel, depression,flute, or the like disposed along the outer annular surface 36. Althoughthe feed grooves 56, 57 are represented as linear elements, it isunderstood that other designs are possible including multi-linear andnon-linear configurations. The feed grooves 56, 57 are separatelyoriented to either side of the central axis 44. The feed grooves 56, 57could be substantially perpendicular or oblique to the rotationaldirection and/or central axis 44, the former represented in FIG. 9.

The dimensions, angular orientation and number of the diagonal grooves43 and feed grooves 56, 57 are design dependent and based in part on thetranslational range of the rotatable runner 35, the widths of theannular seal rings 23, 24, center ring 25 and optional hole 31, theextent of overlap or non-overlap between adjacent groove structures 41,the number of flows from a groove structure 41 required to impinge eachannular seal ring 23, 24, the pressure required to adequately seal theinterface between the rotatable runner 35 and annular seal rings 23, 24,and/or other design factors.

Each diagonal groove 43 further includes at least two optional steps 62a-62 d. Although four steps 62 a-62 d are illustrated along the diagonalgrooves 43 in FIG. 9, it is understood that two or more such steps 62a-62 d may reside along each diagonal groove 43. Each step 62 a-62 dcorresponds to a change in the local depth of the diagonal groove 43relative to the outer annular surface 36. For example, if a diagonalgroove 43 includes two steps 62 a, 62 b, then one step 62 a would have afirst depth and another step 62 b would have a second depth. The depthsdiffer so that one depth is deeper and another depth is shallower. Inpreferred arrangements, the steps 62 a-62 d are arranged so that thechange in local depth from one step to another step results in astepwise variation along the length of each diagonal groove 43.

When the diagonal grooves 43 intersect a first feed groove 56 or asecond feed groove 57, the first step 62 a may be located at the firstfeed groove 56 or the second feed groove 57 and immediately adjacent toand communicable with the next step 62 b along each diagonal groove 43.In other embodiments, two or more steps may reside within the first feedgroove 56 or the second feed groove 57 and at least one step along eachdiagonal groove 43. In yet other embodiments, one step 62 a may residealong the first feed groove 56 or the second feed groove 57 and aportion of one or more diagonal grooves 43 and the remaining step(s) 62b reside(s) exclusively along each diagonal groove 43, as illustrated inFIG. 9. Regardless of the exact arrangement, the steps 62 a-62 d arearranged consecutively to effect a stepwise variation of the depth alongthe length of each groove structure 41.

Referring again to FIG. 9, a gas enters the inlet(s) 26 and is directedinward onto the center ring 25. The gas flows around the center ring 25traversing the gaps between the center ring 25 and the first and secondannular seal rings 23, 24 when the center ring 25 does not include theoptional holes 31. The gas traverses the holes 31 when the center ring25 includes the optional holes 31. Next, the gas impinges along or nearthe feed grooves 56, 57 along outer annular surface 36 of the rotatablerunner 35. The gas is bifurcated by the groove structure 41 so as toseparately enter the first and second feed grooves 56, 57 so that afirst portion is directed into the inlet ends 45 of the left-sidediagonal grooves 43 and a second portion is directed into the inlet ends45 of the right-side diagonal grooves 43. The quantity and/or rate ofgas communicated onto each of the annular seal rings 23, 24 may be thesame or different. The gas traverses the respective diagonal grooves 43and is redirected outward from the rotatable runner 35 at the outlet end46 of each diagonal groove 43. The exits at least one left-side diagonalgroove 43 within a groove structure 41 and impinges the first annularseal ring 23 forming a thin-film layer 20 between the first annular sealring 23 and rotatable runner 35, thereby separating the first annularseal ring 23 from the rotatable runner 35. The gas exits at least oneright-side diagonal groove 43 within a groove structure 41 and impingesthe second annular seal ring 24 forming a thin-film layer 20 between thesecond annular seal ring 24 and rotatable runner 35, thereby separatingthe second annular seal ring 24 from the rotatable runner 35.

Referring now to FIGS. 10-13, several seal assemblies 1 are shown incross-sectional form disposed about a rotatable runner 15, the latterillustrated in side-view form, between a pair of compartments 5, 6. Therotatable runner 15 includes a plurality of groove structures 41. Thegroove structures 41 are arranged circumferentially along the outerannular surface 16 of the rotatable runner 15 immediately adjacent tothe seal assembly 1. The groove structures 41 are positioned so as tocommunicate a gas onto the annular seal rings 3, 4 as the rotatablerunner 15 rotates with respect to the seal assembly 1. In someembodiments, it might be advantageous for adjacent grooves structures 41to partially overlap. In other embodiments, adjacent groove structures41 could be arranged in an end-to-end configuration or with a separationbetween the end of one groove structure 41 and the start of the nextgroove structure 41, the latter represented in FIGS. 10-13.

Each groove structure 41 further includes at least two axial grooves 49disposed about a central axis 44 circumferentially along an outerannular surface 16 of the rotatable runner 15. The axial grooves 49could be aligned symmetrically or non-symmetrically about the centralaxis 44. Each axial groove 49 is a channel, depression, flute, or thelike disposed along the outer annular surface 16. Although the axialgrooves 49 are represented as linear elements, it is understood thatother designs are possible including multi-linear and non-linearconfigurations. The central axis 44 could align with the gap 13 betweenthe first and second annular seal rings 3, 4 or reside adjacent to thefirst and second annular seal rings 3, 4 to allow communication of a gasonto the groove structures 41 over the translational range of therotatable runner 15. The axial grooves 49 are oriented substantiallyparallel to the rotational direction of the rotatable runner 15 and/orthe central axis 44.

At least two axial grooves 49 are disposed along each side of thecentral axis 44. The axial grooves 49 could be substantially parallel toother axial grooves 49 along the same side of the central axis 44 asrepresented by the set of two or more axial grooves 49 along each sideof the central axis 44 in FIGS. 10-13. Two or more of the inlet ends 45and the outlet ends 46 could be aligned circumferentially as representedin FIGS. 10-13. It is also possible for the inlet ends 45 and the outletends 46 to be skewed or staggered and/or and the axial grooves 49 tohave the same or different lengths.

The axial grooves 49 communicate with a feed groove 42 at the inlet ends45 of the axial grooves 49. The feed groove 42 is a channel, depression,flute, or the like disposed along the outer annular surface 16. Althoughthe feed groove 42 is represented as a linear element, it is understoodthat other designs are possible including multi-linear and non-linearconfigurations. The feed groove 42 traverses the central axis 44. Thefeed groove 42 could be substantially perpendicular or oblique to therotational direction and/or central axis 44.

The dimensions, angular orientation and number of the axial grooves 49are design dependent and based in part on the translational range of therotatable runner 15, the widths of the annular seal rings 3, 4, theextent of overlap or non-overlap between adjacent groove structures 41,the number of flows from a groove structure 41 required to impinge eachannular seal ring 3, 4, the pressure required to adequately seal theinterface between the rotatable runner 15 and annular seal rings 3, 4,and/or other design factors.

An optional windback thread 47 could extend from the annular sealhousing 2 in the direction of the second compartment 6. The windbackthread 47 is an element known within the art that utilizes the shearforces produced by a rotating shaft to circumferentially wind a fluidalong one or more threads. The threads are disposed along the innerannular surface of the windback thread 47 and oriented so that a fluidenters the threads and is directed away from the annular seal rings 3, 4within a seal assembly 1. The windback thread 47 could be machined intothe annular seal housing 2 or mechanically attached or fastened theretoas a separate element via methods understood in the art. The windbackthread 47 is disposed about the runner 15 so as to overlay the runner 15without contact. A plurality of optional slots 48 are positioned alongone end of the rotatable runner 15 adjacent to the windback thread 47.The slots 48 could interact with the windback thread 47 to sling a fluidaway from the annular seal rings 3, 4 in the direction of the secondcompartment 6. Although shown with several embodiments, it is understoodthat an optional windback thread 47 is applicable to other embodimentsdescribed herein.

In some embodiments, it might be advantageous to taper the axial grooves49 as represent in FIG. 11. The axial groove 49 could include a width atthe inlet end 45 that is greater than the width at the outlet end 46 sothat the width decreases with distance along the axial groove 49. Thisarrangement progressively reduces the volume through which the gaspasses causing a gas to compress with distance along the axial groove49, thereby further increasing the pressure otherwise achieved along anaxial groove 49 with uniform width. This effect is also possible bytapering the axial groove 49 depthwise along the length of the axialgroove 49 so that the depth at the inlet end 45 is greater than thedepth at the outlet end 46.

In yet other embodiments, the groove structures 41 could vary widthwiseas represented in FIGS. 12 and 13. The width between adjacent groovestructures 41 could differ so that the axial width W₁ of one groovestructure 41 is greater than the axial width W₂ of the next groovestructure 41 resulting in an overhang 50. The overhang 50 facilitates astaggered arrangement of axial grooves 49 between adjacent groovestructures 41 when the total number of axial grooves 49 is the same ineach groove structure 41 as represented in FIG. 12 and when the totalnumbers of axial grooves 49 differ between groove structures 41 asrepresented in FIG. 13. Both embodiments increase sealing effects over agreater range of translations by a rotatable runner 15.

Each axial groove 49 further includes at least two optional steps 62a-62 d. Although four steps 62 a-62 d are illustrated along the axialgrooves 49 in FIGS. 10-13, it is understood that two or more such steps62 a-62 d may reside along each axial groove 49. Each step 62 a-62 dcorresponds to a change in the local depth of the axial groove 49relative to the outer annular surface 16. For example, if an axialgroove 49 includes two steps 62 a, 62 b, then one step 62 a would have afirst depth and another step 62 b would have a second depth. The depthsdiffer so that one depth is deeper and another depth is shallower. Inpreferred arrangements, the steps 62 a-62 d are arranged so that thechange in local depth from one step to another step results in astepwise variation along the length of each axial groove 49.

When the axial grooves 49 intersect a feed groove 42, the first step 62a may be located at the feed groove 42 and immediately adjacent to andcommunicable with the next step 62 b along each axial groove 49. Inother embodiments, two or more steps may reside within the feed groove42 and at least one step along each axial groove 49. In yet otherembodiments, one step 62 a may reside along the feed groove 42 and aportion of one or more axial grooves 49 and the remaining step(s) 62 breside(s) exclusively along each axial groove 49, as illustrated inFIGS. 10-13. Regardless of the exact arrangement, the steps 62 a-62 dare arranged consecutively to effect a stepwise variation of the depthalong the length of each groove structure 41.

Referring again to FIGS. 10-13, a gas enters the inlet(s) 9 and isdirected into the gap 13 between the annular seal rings 3, 4. The gastraverses the gap 13 thereafter impinging the feed groove 42 along outerannular surface 16 of the rotatable runner 15. The gas is bifurcatedalong the feed groove 42 allowing the gas to enter the inlet ends 45 sothat a first portion is directed into the left-side axial grooves 49 anda second portion is directed into the right-side axial grooves 49. Thequantity and/or rate of gas communicated onto each of the annular sealrings 3, 4 may be the same or different. The gas traverses therespective axial grooves 49 and is redirected outward from the rotatablerunner 15 at the outlet end 46 of each axial groove 49. The gas exits atleast one left-side axial groove 49 within a groove structure 41 andimpinges the first annular seal ring 3 forming a thin-film layer 20between the first annular seal ring 3 and rotatable runner 15, therebyseparating the first annular seal ring 3 from the rotatable runner 15.The gas exits at least one right-side axial groove 49 within a groovestructure 41 and impinges the second annular seal ring 4 forming athin-film layer 20 between the second annular seal ring 4 and rotatablerunner 15, thereby separating the second annular seal ring 4 from therotatable runner 15.

In some embodiments, it might be advantageous to direct a gas throughthe rotatable runner 15 or 35 rather than or in addition to between thefirst and second annular seal rings 3, 4 or 23, 24.

Referring now to FIGS. 14 and 15, a seal assembly 21 is shown incross-sectional form disposed about a rotatable runner 35, the latterillustrated in side-view form, between a first compartment 58 and asecond compartment 59. The first and second compartments 58, 59 couldinclude a low pressure gas. Gas within the second compartment 59 couldbe at a higher pressure than the first compartment 58. One or bothcompartments 58, 59 could further include a lubricant. The annular sealhousing 22 could include an optional windback thread 47 as illustratedin FIGS. 10-13.

The rotatable runner 35 includes a plurality of groove structures 41 andcould further include an optional flange 60. The groove structures 41are arranged circumferentially along the outer annular surface 36 of therotatable runner 35 immediately adjacent to the seal assembly 21. Thegroove structures 41 are positioned so as to communicate a gas onto theannular seal rings 23, 24 as the rotatable runner 35 rotates withrespect to the seal assembly 21. While FIG. 14 shows bifurcated groovestructures 41, it is understood that all groove structures 17, 37, 41,55 described herein are applicable to embodiments wherein a gas isdirected through a rotatable runner 15, 35. An optional center ring 25could be interposed between the first and second annular seal rings 23,24, as otherwise described herein. It is likewise possible for the sealassembly 21 to not include a center ring 25, as also described herein.

A plurality of through holes 61 are separately disposed about thecircumference of the rotatable runner 35, as represented in FIGS. 14 and15. Each through hole 61 could traverse the rotatable runner 35 so as toallow passage of a gas along one side of the rotatable runner 35 toanother side of the rotatable runner 35, preferably from a regionadjacent to the inner portion of the rotatable runner 35 and onto theouter annular surface 36 of the rotatable runner 35 adjacent to thegroove structures 41 and the first and second annular seal rings 23, 24.

The number, size, shape, location, and arrangement of the through holes61 should allow communication of a gas through the rotatable runner 35and onto the outer annular surface 36 so as to form a thin-film layer 20between the first and second annular seal rings 23, 24 and the rotatablerunner 35. In some embodiments, it might be advantageous for eachthrough hole 61 to be elongated along the central axis 44 and alignedtherewith with one such through hole 61 interposed between each pairedarrangement of diagonal grooves 43, as represented in FIG. 14. Otherconfigurations are possible.

Each diagonal groove 43 further includes at least two optional steps 62a-62 d. Although four steps 62 a-62 d are illustrated along eachdiagonal groove 43 in FIG. 14, it is understood that two or more suchsteps 62 a-62 d may reside along each diagonal groove 43. Each step 62a-62 d corresponds to a change in the local depth of the diagonal groove43 relative to the outer annular surface 36. For example, if a diagonalgroove 43 includes two steps 62 a, 62 b, then one step 62 a would have afirst depth and another step 62 b would have a second depth. The depthsdiffer so that one depth is deeper and another depth is shallower. Inpreferred arrangements, the steps 62 a-62 d are arranged so that thechange in local depth from one step to another step results in astepwise variation along the length of each diagonal groove 43.Regardless of the exact arrangement, the steps 62 a-62 d are arrangedconsecutively to effect a stepwise variation of the depth along thelength of each groove structure 41.

Referring again to FIGS. 14 and 15, a gas enters the through holes 61along the rotatable runner 35 and is directed outward in the directionof the first and second annular seal rings 23, 24 with or without thecenter ring 25. The gas flows onto the rotatable runner 35 so as toimpinge the outer annular surface 36 of the rotatable runner 35,preferably at or near the inlet ends 45. The gas is bifurcated by thegroove structure 41 at the inlet ends 45 so that a first portion isdirected into the left-side diagonal grooves 43 and a second portion isdirected into the right-side diagonal grooves 43. The quantity and/orrate of gas communicated onto each of the annular seal rings 23, 24 maybe the same or different. The gas traverses the respective diagonalgrooves 43 and is redirected outward from the rotatable runner 35 at theoutlet end 46 of each diagonal groove 43. The gas exits at least oneleft-side diagonal groove 43 within a groove structure 41 and impingesthe first annular seal ring 23 forming a thin-film layer 20 between thefirst annular seal ring 23 and rotatable runner 35, thereby separatingthe first annular seal ring 23 from the rotatable runner 35. The gasexits at least one right-side diagonal groove 43 within a groovestructure 41 and impinges the second annular seal ring 24 forming athin-film layer 20 between the second annular seal ring 24 and rotatablerunner 35, thereby separating the second annular seal ring 24 from therotatable runner 35.

As described herein, a gas enters the diagonal or axial groove 19, 38,43 49 so that some or all of the gas entering the groove 19, 38, 43, 49either partially or completely traverses the length thereof. The inwardflow of the gas results in a pressure gradient. The result is a pressureprofile that steadily increases along the length of the groove 19, 38,43, 49 so that the pressure downstream is generally higher than thepressure upstream. The pressure profile may be linear, non-linear, or acombination thereof.

Referring now to FIGS. 16 and 17, exemplary radial and axial grooves 19,38, 43, 49 with four steps 62 a-62 d and five steps 62 a-62 e,respectively, are shown in an end-to-end configuration along the outerannular surface 16, 36 of a rotatable runner 15, 35. The steps 62 a-62d, 62 a-62 e form a single pocket-like structure that opens outward inthe direction of the outer annular surface 16, 36. FIG. 16 illustratesthe stepwise orientation of the steps 62 a-62 d whereby the first step62 a, second step 62 b, third step 62 c, and fourth step 62 d separatelyextend into the rotatable runner 15, 35 at four depths h_(a), h_(b),h_(c), h_(d), respectively. FIG. 17 illustrates the stepwise orientationof the steps 62 a-62 e whereby the first step 62 a, second step 62 b,third step 62 c, fourth step 62 d, and fifth step 62 e separately extendinto the rotatable runner 15, 35 at five depths h_(a), h_(b), h_(c),h_(d), h_(e) respectively. In preferred embodiments, the depths h_(a),h_(b), h_(c), h_(d) should decrease incrementally(h_(a)>h_(b)>h_(c)>h_(d)) in the direction opposite of the rotationaldirection of the rotatable runner 15, 35. However, it is only requiredthat at least one downstream step 62 b-62 d be at a depth less than oneupstream step 62 a-62 c. In other embodiments, it might be advantageousto include at least one downstream step 62 b-62 e at a depth h_(b),h_(c), h_(d), h_(e) greater than the depth h_(a), h_(b), h_(c), h_(d) ofat least one upstream steps 62 a-62 d.

Referring again to FIGS. 16 and 17, the depths h_(a), h_(b), h_(c),h_(d), h_(e) generally represent the distance from the outer annularsurface 16, 36 to the base 63 a-63 e of each respective step 62 a-62 e,although other methods of determining the depths h_(a), h_(b), h_(c),h_(d), h_(e) are possible. Each base 63 a-63 e is defined by a surfaceof generally planar extent along the rotatable runner 15, 35; however,other shapes are possible. The bases 63 a-63 e may be oriented so thattwo or more such bases 63 a-63 e are parallel, as shown in FIGS. 16 and17. Regardless of the shape and orientation of each base 63 a-63 e, thetransition from one step 62 a-62 d to another step 62 b-62 e defines abase shoulder 64. The base shoulder 64 represents an abrupt change ordiscontinuity in the depth profile between the inlet and outlet end ofthe diagonal groove 19, 38, 43 and the axial groove 49.

As the rotatable runner 15, 35 rotates, a gas adjacent to orcommunicated onto the rotatable runner 15, 35 flows into and along thesteps 62 a-62 e in the direction opposite to the rotational direction ofthe rotatable runner 15, 35. In addition to or in place of the flowpatterns implemented by the various groove structures 17, 37, 41, 55 asotherwise described herein, interaction between the gas and each baseshoulder 64 redirects the circumferential flow along each step 62 a-62 eso that some or all of the gas is locally directed radially outwardtoward the first and second annular seal rings 3, 4 or 23, 24. Theresult is turbulent and/or non-turbulent flow adjacent to each baseshoulder 64 causing localized pressure discontinuities along thepressure profile described herein that enhance the thin-film layer 20formed between the outer annular surface 16, 36 and first and secondannular seal rings 3, 4 or 23, 24. The enhanced stiffness of theresultant thin-film layer 20 allows for higher operating differentialpressures without the seal contacting the runner which extends seal lifeand lowers heat generation. The gas that leaks thru the thin-film layer20 prevents or minimizes a lubricant from leaking into the sealingchamber and/or entering one or both lower pressure compartments 5, 6.

Referring now to FIG. 18, a groove 19, 38, 43, 49 is shown along theouter annular surface 16, 36 of a rotatable runner 15, 35. The groove19, 38, 43, 49 is shown with steps 62 a-62 d arranged stepwise so thatthe deepest step 62 a is at the leftmost or upstream end and theshallowest step 62 d is at the rightmost or downstream end. The groove19, 38, 43, 49 is defined to include a length (L) centered with thecenterline 14, 34 so that one-half of the length (L) is to the left ofthe centerline 14, 34 and one-half of the length (L) is to the right ofthe centerline 14, 34. Each step 62 a-62 d has a unique depth (h)whereby the deepest groove defines the maximum depth (h_(max)) and theshallowest groove defines the minimum depth (h_(min)). The left end ofthe leftmost step 62 a and the right end of the rightmost step 62 dintersect the outer annular surface 16, 36 thereby defining a line 65.The line 65 intersects the radial distance (r), drawn from thecenterline 14, 34, at a right angle.

The location of each base 63 a-63 e may be defined as by distance ratio(R) representing the radial distance (r) adjusted by the depth (h) of astep 62 a-62 e over the runner radius r_(r). The distance ratio (R) iscalculated by the equation

$\begin{matrix}{R = \frac{r - h}{r_{r}}} & (1)\end{matrix}$

where r is further calculated by the equation

$\begin{matrix}{r = \sqrt{r_{r}^{2} - \left( \frac{L}{2} \right)^{2}}} & (2)\end{matrix}$

whereby the combination of equations (1) and (2) yields the equation

$\begin{matrix}{R = \frac{\sqrt{\left( {r_{r}^{2} - \left( \frac{L}{2} \right)^{2}} \right.} - h}{r_{r}}} & (3)\end{matrix}$

For purpose of Equation (3), the length (L) corresponds to the chord orcircumferential length as described in FIGS. 19a and 19b after allappropriate adjustments (if required) and the depth (h) of a groove 62a-62 e corresponds to the vertical distance between line 65 and the base63 a-63 e. If the base 63 a-63 e is non-planar or angled, then a maximumdepth or an average depth may be appropriate for calculational purposes.The lower and upper bounds for the distance ratio (R) for a groove 19,38, 43, 49 are calculable for a given length (L) and runner radius(r_(r)) where the lower distance ratio (R_(L)) corresponds to themaximum depth (h_(max)) and the upper distance ratio (R_(U)) correspondsto the minimum depth (h_(min)).

It may be advantageous in some applications to include one or moreshoulders along both bottom wall and side walls of a hydrodynamic groovewithin a groove structure. These multi-axis stepped grooves, severalexamples illustrated in FIGS. 20a-28g , are applicable to the variousembodiments described herein. While various embodiments of multi-axisstepped grooves described with reference to two grooves intersecting andcommunicable with a feed groove, it is understood that the scope ofgroove structures includes two or more grooves with or without a feedgroove.

Referring now to FIGS. 20a-21b , a groove structure 66 is positionedalong the outer annular surface 68 of a rotatable runner 67 whereby thegroove structure 66 includes grooves 69 which intersect a feed groove70. Although one groove structure 66 is illustrated for descriptivepurposes in FIGS. 20a-27b , it is understood that a plurality of suchgroove structures 66 are situated about the outer annular surface 68,such as shown in FIGS. 2, 3, and 5-14, so as to properly maintain athin-film layer between a runner and a paired arrangement of seal rings.

Referring again to FIGS. 20a-21b , the feed groove 70 is communicablewith the grooves 69 so that a gas entering the feed groove 70 thereafterflows into each groove 69. The resultant flow pattern requires the gaswithin the feed groove 70 to be separated so that a portion of the gasenters each groove 69. The grooves 69 are positioned with respect to thefeed groove 70 so that the gas portion flows into and then along eachgroove 69 from an upstream end 81 to a downstream end 82. The resultantflow pattern is in a direction opposite to the rotation direction of therotatable runner 67.

Referring again to FIGS. 20a-21b , each groove 69 includes two or moresteps 71, although three steps 71 are illustrated by way of example.Each step 71 includes and is defined by a base wall 72 which correspondsto the bottom of the groove 69. Base walls 72 are situated relative toone another so that the effective groove depth D_(G) decreases along thegroove 69 from the upstream end 81 to the downstream end 82. Each twoadjoining steps 71 are separated by a base shoulder 73. The baseshoulder 73 is an abrupt change or discontinuity in the depth profile ofthe groove 69. The base shoulder 73 is disposed between a pair of basewalls 72 so that the deeper end of the base shoulder 73 contacts thedownstream side of one base wall 72 and the less deep end of the baseshoulder 73 contacts the upstream side of another base wall 72. Anadditional base shoulder 73 may be positioned at the downstream end 82to terminate the groove 69. The resulting profile formed by the basewalls 72 and the base shoulders 73 defines the floor or base portion ofa groove 69. In some embodiments, a base shoulder 73 may be located atthe interface between the feed groove 70 and a groove 69, as illustratedin FIGS. 20a-21b . In other embodiments, the depths of the feed groove70 and a groove 69 at the inlet end of the groove structure 66 may bethe same so that the transition avoids a base shoulder 73 therebetween,as illustrated in FIGS. 25a -27 b.

Referring again to FIGS. 20a-21b , each groove 69 further includes apair of side walls 74. The side walls 74 are disposed about andintersect two or more base walls 72 to define the shape of a groove 69.Each side wall 74 may include one or more side shoulders 75. A sideshoulder 75 is an abrupt change or discontinuity in the width profile ofthe groove 69. The side shoulder 75 is disposed along a side wall 74 sothat the groove width W_(G) upstream from the side shoulder 69 is widerthan the groove width W_(G) downstream from the side shoulder 69. Theresulting profile formed by each side wall 74 and corresponding sideshoulder(s) 75 define the lateral bounds of a groove 69 whereby theeffective groove width W_(G) decreases along the groove 69 from theupstream end 81 to the downstream end 82.

Referring now to FIGS. 20a, 20b and 28c , side shoulders 75 may besituated so as to intersect the base shoulder 73. The side shoulders 75are aligned in an opposed arrangement whereby one side shoulder 75 alongone side wall 74 is directly across from another side shoulder 75 alonganother side wall 74. The side shoulders 75 are further aligned with thebase shoulder 73 forming a substantially U-shaped wall along a planewhich intersects a groove 69 between two adjoining steps 71, asgenerally illustrated in FIG. 28c . A narrowing of both the groove depthD_(G) between adjoining steps 71 via a base shoulder 73 and the groovewidth W_(G) between adjoining steps 71 via the side shoulders 75 reducesthe local volume from one step 71 to another step 71 causing acorresponding increase in the effective local pressure of the gas in thedownstream step(s) 71. This higher effective pressure improves thestiffness and sealing properties of a thin film, an example of thelatter being the thin-film layer 20 between runner and sealing ringsillustrated in FIGS. 2-3 and 5-15.

Referring now to FIGS. 21a, 21b, 28a and 28b , side shoulders 75 may besituated in an offset arrangement with respect to a base shoulder 73. Inthese embodiments, the base shoulder 73 is disposed between a pair ofside shoulders 75 along each side wall 74. Two side shoulders 75 arealigned in an opposed arrangement along a plane which bisects the groove69 upstream from the base shoulder 73 whereby one side shoulder 75 alongone side wall 74 is directly across from another side shoulder 75 alonganother side wall 74. Two other side shoulders 75 are aligned in anopposed arrangement along a plane which bisects the groove 69 downstreamfrom the base shoulder 73 whereby one side shoulder 75 along one sidewall 74 is directly across from another side shoulder 75 along anotherside wall 74. The separation between base shoulder 73 and paired sideshoulders 75 results in a decrease in the groove depth D_(G) at theinterface between adjoining steps 71 as illustrated in FIG. 28a and adecrease in the groove width W_(G) both upstream and downstream from thebase shoulder 73 as illustrated FIG. 28b . The bifurcated narrowingcauses corresponding increases in the effective local pressure of thegas along each step 71 and between adjoining steps 71.

Referring now to FIGS. 22, 28 a, 28 d and 28 e, side shoulders 75 may besituated in an offset arrangement with respect to the base shoulder 73.In these embodiments, the base shoulder 73 is disposed between a pair ofside shoulders 75 along each side wall 74. Two side shoulders 75 arealigned in an offset arrangement upstream from the base shoulder 73whereby one side shoulder 75 along one side wall 74 is not directlyacross from another side shoulder 75 along another side wall 74. Twoother side shoulders 75 are aligned in an offset arrangement downstreamfrom the base shoulder 73 whereby one side shoulder 75 along one sidewall 74 is not directly across from another side shoulder 75 alonganother side wall 74. The separation between base shoulder 73 and sideshoulders 75 causes a decrease in the groove depth D_(G) at theinterface between adjoining steps 71 as illustrated in FIG. 28a andcauses a two-step decrease in the groove width W_(G) upstream anddownstream from the base shoulder 73 as generally illustrated in FIGS.28d and 28e . The separate and bifurcated narrowing causes correspondingincreases in the effective local pressure of the gas along each step 71and between adjoining steps 71.

Referring now to FIGS. 23, 28 d, 28 e, 28 f, and 28 g, side shoulders 75may be situated in an intersecting arrangement and an offset arrangementwith respect to the base shoulder 73. In these embodiments, one sideshoulder 73 intersects the base shoulder 75 along one side wall 74 andthe base shoulder 73 is disposed between a pair of side shoulders 75along another side wall 74. For the paired side shoulders 75, one sideshoulder 75 is upstream and another side shoulder 75 is downstream fromthe intersecting base shoulder 73 and side shoulder 75. The intersectingbase shoulder 73 and side shoulder 75 causes a decrease in the groovedepth D_(G) and the groove width W_(G) at the interface betweenadjoining steps 71 as illustrated in FIG. 28f or 28 g. Each remainingside shoulders 75 causes a decrease in the groove width W_(G) upstreamand downstream from the base shoulder 73 as generally illustrated inFIG. 28d or 28 e. The separate and bifurcated narrowing causescorresponding increases in the effective local pressure of the gas alongeach step 71 and between adjoining steps 71.

Referring now to FIGS. 24, 28 a, 28 d and 28 e, side shoulders 75 may besituated in an offset arrangement with respect to the base shoulder 73.In these embodiments, the base shoulder 73 is disposed between a pair ofside shoulders 75. One side shoulder 75 is upstream along one side wall74 and another side shoulder 75 is downstream along another side wall74. The separation between the base shoulder 73 and side shoulders 75causes a decrease in the groove depth D_(G) at the interface betweenadjoining steps 71 as illustrated in FIGS. 28a . The offset arrangementbetween a side shoulder 75 and the base shoulder 73 causes a decrease inthe groove width W_(G) upstream and downstream from the base shoulder 73as generally illustrated in FIGS. 28d and 28e . The separate andbifurcated narrowing causes corresponding increases in the effectivelocal pressure of the gas along each step 71 and between adjoining steps71.

Referring again to FIG. 22, a groove 69 with an asymmetric, steppedprofile may be positioned at two or more locations along a feed groove70 so to form a groove structure 66 which is likewise asymmetric. Inthese embodiments, the groove 69 is repeated along the feed groove 70without inversion.

Referring again to FIGS. 23 and 24, a groove 69 with an asymmetric,stepped pattern may be positioned at two or more locations along a feedgroove 70 so to form a groove structure 66 which is symmetric, that isthe left-side groove 69 is a mirror image of the right-side groove 69.In these embodiments, the groove 69 is repeated along the feed groove 70with appropriate inversion.

Referring now to FIGS. 20a -24, both side walls 74 and base walls 72 maybe oriented in a parallel configuration regardless of the number,location(s) and dimensional properties of side shoulders 75 and baseshoulders 73. The resultant profiles cause an abrupt reduction, to anotherwise uniform cross-sectional area along a groove 69, after thelocation of each side shoulder(s) 75 and/or each base shoulder(s) 73.Each abrupt decrease in cross-sectional area corresponds to an abruptincrease in both velocity and pressure of the gas. In other embodiments,it may be advantageous to include additional features to the variousgrooves described herein which permit for a more continuous reduction inthe cross-sectional area along other portions of a groove.

Referring now to FIGS. 25a and 25b , the base walls 72 may be tapered sothat the cross-sectional area along a step 71 gradually decreases fromupstream to downstream. In these embodiments, the step 71 is tapered sothat the depth at the upstream side is greater than the depth at thedownstream side. One or more base shoulders 73 disposed between two ormore base walls 72 and/or one or more side shoulders 75 along one orboth side walls 74 may facilitate abrupt changes in the cross-sectionalarea along a groove 69 as required by the application. The side walls 74may be disposed in a parallel arrangement regardless of the location ofthe side shoulders 75 so that changes to the cross-section area along agroove 69 are determined by the taper of the base wall 72, the number,location and dimensions of the base shoulder(s) 73, and the number,location and dimensions of the side shoulder(s) 75.

Referring now to FIGS. 26a and 26b , the side walls 74 may be tapered sothat the cross-sectional area along at least a portion of each step 71gradually decreases from upstream to downstream. A side wall 74 istapered in part or whole so that the upstream width of a groove 69 isgreater than the downstream width of the same groove 69. One or morebase shoulders 73 disposed between two or more base walls 72 and/or oneor more side shoulders 75 along one or both side walls 74 may facilitateabrupt changes in the cross-sectional area along a groove 69 as requiredby the application. The base walls 72 may be disposed in a parallelarrangement regardless of the location of the base shoulders 73 so thatchanges to the cross-section area along a groove 69 are determined bythe taper of each side wall 74, the number, location and dimensions ofthe base shoulder(s) 73, and the number, location and dimensions of theside shoulder(s) 75.

Referring now to FIGS. 27a and 27b , both base walls 72 and side walls74 may be tapered as otherwise separately described in FIGS. 25a-26b sothat the cross-sectional area along each step 71 gradually decreasesfrom upstream to downstream. Base shoulder(s) 73 and/or side shoulder(s)75 may facilitate abrupt changes in the cross-sectional area along agroove 69 as required by the application. Resultant changes to thecross-section area along a groove 69 are determined by the degree oftaper for the base walls 72 and each side wall 74, the number, locationand dimensional properties of the base shoulder(s) 73, and the number,location and dimensional properties of the side shoulder(s) 75.

Referring again to FIGS. 27a and 27b , a source flow 83 is communicatedinto the feed groove 70. The source flow 83 may corresponds to the gaswhich passes between the annular seal rings 3, 4 as generallyillustrated in FIG. 10 or which exits through holes 61 along a rotatablerunner 35 as illustrated in FIG. 15. The source flow 83 will prefer toexit the feed groove 70 causing flow into the grooves 69. Beforeentering the grooves 69, the source flow 83 is separated so that aportion of the gas entering the feed groove 70 is directed into eachgroove 69. By way of example, the source flow 83 is separated into afirst portion 76 which flows into one groove 69 and a second portion 77which flows into a second groove 69 when the feed groove 70 iscommunicable with two grooves 69. After entering each groove 69, thefirst portion 76 and the second portion 77 generally prefer a pathwayfrom the upstream end 81 to the downstream end 82 thereby establishing alongitudinal flow 80, which is also understood to be circumferential inform, in each groove 69. The longitudinal flow 80 traverses the groove69 so as to interact with parallel and tapered features of the base wall72 and side walls 74, base shoulder(s) 73 between adjacent base walls72, and side shoulder(s) 75 along side walls 74. Each interaction mayredirect the flow and increase both velocity and pressure of at least aportion of the longitudinal flow 80.

Referring now to FIGS. 27a and 28a , the transition between adjoiningsteps 71 may include only a base shoulder 73 disposed between a pair ofbase walls 72. At least a portion of the longitudinal flow 80 whichinteracts with, that is flows into or is impeded by, the base shoulder73 is locally redirected as an outward radial flow 78. The outwardradial flow 78 is locally redirected so as to be generally perpendicularto the longitudinal flow 80 adjacent to the base shoulder 73. Theresultant flow enhance the stiffness of a thin film produced along theannular seal rings 3, 4 by the groove structures 66. The cross-sectionalarea of the groove 69 is reduced by the area corresponding to the baseshoulder depth D_(B) as the longitudinal flow 80 flows from a step 71with a deeper base 72 to a next step 71 with a less deep base 72. Thesmaller cross-sectional area causes a corresponding increase to thevelocity and pressure of the gas immediately after the base shoulder 73.

Referring now to FIGS. 27a and 28b , a pair of side shoulders 75 may bedisposed along a pair of side walls 74. At least a portion of thelongitudinal flow 80 which interacts with, that is flows into or isimpeded by, each side shoulder 75 is locally redirected as a lateralflow 79. Each lateral flow 79 is locally redirected so as to begenerally perpendicular to the longitudinal flow 80 adjacent to the sideshoulders 75. The resultant flow pattern may cause the lateral flows 79to interact, that is converge, thereby enhancing the stiffness of a thinfilm produced along the annular seal rings 3, 4 by the groove structures66. The cross-sectional area of the groove 69 is reduced by the areascorresponding to the step shoulder depth D_(S) as the longitudinal flow80 flows from a wider portion of a step 71 to a less wide portion of thesame step 71. The smaller cross-sectional area causes a correspondingincrease to the velocity and pressure of the gas immediately after thestep shoulders 75.

Referring now to FIGS. 27a and 28c , the transition between adjoiningsteps 71 may include a base shoulder 73 disposed along a base wall 72and a pair of side shoulders 75 disposed between a pair of side walls74. At least a portion of the longitudinal flow 80, which interacts with(either flows into or is impeded by) the base shoulder 73, is locallyredirected as an outward radial flow 78 as described above for FIG. 28a. At least a portion of the longitudinal flow 80, which interacts with(flows into or is impeded by) each side shoulder 75, is locallyredirected as a lateral flow 79 as described above for FIG. 28b . Theresultant flow patterns may cause the outward radial flow 78, thelateral flows 79, and the longitudinal flow 80 to interact, that isconverge, thereby enhancing the stiffness of a thin film produced alongthe annular seal rings 3, 4 by the groove structures 66. Thecross-sectional area of the groove 69 is reduced by the areascorresponding to the base shoulder depth D_(B) and both side shoulderdepths D_(S) as the longitudinal flow 80 traverses from one step 71 intoanother step 71. The smaller cross-sectional area causes a correspondingincrease to the velocity and pressure of the gas immediately after thebase shoulder 73 and the step shoulders 75.

Referring now to FIGS. 27a, 28d and 28e , a side shoulder 75 may bedisposed along a left side wall 74 as in FIG. 28d or a right side wall74 as in FIG. 28e . At least a portion of the longitudinal flow 80,which interacts with a side shoulder 75, is locally redirected as alateral flow 79 in the direction of the side wall 74 withoutcorresponding side shoulder 75. The lateral flow 79 is locallyredirected so as to be generally perpendicular to the longitudinal flow80 adjacent to the side shoulder 75. In some embodiments, the lateralflow 79 may impinge the side wall 74 opposite of the side shoulder 75.The resultant flow pattern may enhance the stiffness of a thin filmproduced along the annular seal rings 3, 4 by the groove structures 66.The cross-sectional area of the groove 69 is reduced by the areascorresponding to the step shoulder depth D_(S) as the longitudinal flow80 passes from a wider portion of a step 71 to a less wide portion ofthe same step 71. The smaller cross-sectional area causes acorresponding increase to the velocity and pressure of the gasimmediately after the base shoulder 73.

Referring now to FIGS. 27a, 28f and 28g , the transition betweenadjoining steps 71 may include a base shoulder 73 disposed along a basewall 72 and either a left side shoulder 75 disposed along a side wall 74as in FIG. 28f or a right side shoulder 75 disposed along a side wall 74as in FIG. 28g . At least a portion of the longitudinal flow 80, whichinteracts with the base shoulder 73, is locally redirected as an outwardradial flow 78 as described for FIG. 28a . At least a portion of thelongitudinal flow 80, which interacts with a side shoulder 75, islocally redirected as a lateral flow 79 as described for either FIG. 28dor FIG. 28e . The resultant flow patterns may cause the outward radialflow 78, the lateral flow 79, and the longitudinal flow 80 to interact,that is converge, with or without further interaction with orimpingement of the side wall 74 without a side shoulder 75, therebyenhancing the stiffness of a thin film produced along the annular sealrings 3, 4 by the groove structures 66. The cross-sectional area of thegroove 69 is reduced by the areas corresponding to the base shoulderdepth D_(B) and one side shoulder depth D_(S) as the longitudinal flow80 traverses from one step 71 into another step 71. The smallercross-sectional area causes a corresponding increase to the velocity andpressure of the gas immediately after the base shoulder 73 and the stepshoulders 75.

Features of the groove structure 66 and the grooves 69 with base andlateral steps, in particular, are applicable to the various otherembodiments described herein so as to form a thin film between a pair ofannular seal rings 3, 4 and rotatable runners 15, 35, 67. By way ofexample and reference to FIGS. 27a-28g , the source flow 83 may becommunicated into a feed groove 70 communicable with at least twogrooves 69. The flow source 83 may be a gas which originates eitheradjacent to the annular seal rings 3, 4 as provided for in FIGS. 1-13 orfrom a source within the rotatable runner 67 as provided for in FIGS. 14and 15. The communicability between feed groove 70 and grooves 69 may bepermitted by intersecting contact therebetween. Each groove 69 includesan upstream end 81 and a downstream end 82 generally aligned along therotation direction of the rotatable runner 67. Portions of the sourceflow 83 entering the feed groove 70 separately flow into the grooves 69.The resultant flow pattern between feed groove 70 and grooves 69requires a separation of the source flow 83 at the upstream ends 81 ofthe grooves 69. The separation may be permitted by an opening at theinterface between the feed groove 70 and each groove 69 and/or theoverall geometric configuration therebetween. The portion of the sourceflow 83 entering each groove 69 is then directed by the base walls 72and the side walls 74 from the upstream end 81 to the downstream end 82.The axial flow of gas along each groove 69 establishes the longitudinalflow 80 therein. The floor of each groove 69 may include at least twobase walls 72 whereby each adjacent pair of base walls 72 is disposedabout a base shoulder 73. The base shoulder 73 facilitates a radialtranslation whereby the upstream base wall 72 is deeper than thedownstream base wall 72. A portion of the longitudinal flow 80 may flowinto the base shoulder 73 so as to interact therewith resulting in aredirection of the flow vector whereby the affected longitudinal flow 80flows radially outward from the groove 69 as an outward radial flow 78.Each side wall 74 along a groove 69 may include one or more sideshoulders 75 which facilitate an axial translation whereby the upstreamwidth of the groove 69 is less than the downstream width. A portion ofthe longitudinal flow 80 may flow into the side shoulder 75 so as tointeract therewith resulting in a redirection of the flow vector wherebythe affected longitudinal flow 80 flows transversely within the groove69 as a lateral flow 79. The resultant lateral flow(s) 79 and outwardradial flow(s) 78 are perpendicular to one another and to thelongitudinal flow.

Referring now to FIGS. 28c, 28f, and 28g , one or more lateral flow(s)79 and the outward radial flow 78 may converge after redirection by theside shoulder(s) 75 and the base shoulder 73, respectively. In preferredembodiments, convergence occurs when the side shoulder(s) 75 and thebase shoulder 73 intersect along a plane which traverses a groove 69.The convergence may result in a mixing or subsequent redirection of theflow streams with or without the longitudinal flow 80 thereafterfacilitating enhancement to the stiffness of a thin-film layer betweensealing rings and runner.

Referring now to FIGS. 20a-27b , one or more lateral flow(s) 79 may beformed downstream and/or upstream with respect to an outward radial flow78. In preferred embodiments, a lateral flow 79 formed via a sideshoulder 75 along one side wall 74 may be directed into the other sidewall 74. The resultant impingement may cause a mixing or subsequentredirection of or by the impinging flow so as to enhance the stiffnessof a thin-film layer between sealing rings and runner.

Referring now to FIG. 28b , a pair of lateral flows 79 may convergeafter redirection by a pair of opposed side shoulders 75. In preferredembodiments, convergence occurs when the side shoulders 75 intersectalong a plane which traverses a groove 69. The convergence may result ina mixing or subsequent redirection of the two flow streams with orwithout the longitudinal flow 80 facilitating enhancement to thestiffness of a thin-film layer between sealing rings and runner.

The grooves with base and lateral steps described herein are alsoapplicable to embodiments wherein a plurality of single grooves with orwithout feed groove are disposed about a rotatable runner to form a thinfilm which seals the interface between one annular seal ring and therunner.

The description above indicates that a great degree of flexibility isoffered in terms of the present invention. Although various embodimentshave been described in considerable detail with reference to certainpreferred versions thereof, other versions are possible. Therefore, thespirit and scope of the appended claims should not be limited to thedescription of the preferred versions contained herein.

What is claimed is:
 1. A circumferential seal assembly with bifurcatedflow comprising: (a) an annular seal housing disposed between a pair ofcompartments; (b) a rotatable runner; (c) a pair of annular seal ringsdisposed within said annular seal housing and disposed about saidrotatable runner; and (d) a plurality of groove structures disposedalong an outer annular surface of said rotatable runner, each saidgroove structure includes at least two grooves intersecting a feedgroove, each said groove structure separates a source flow communicatedinto said feed groove so that a portion of said source flow enters eachsaid groove to form a longitudinal flow therein, each said grooveincludes at least two adjoining steps whereby each said step is definedby a base wall, said base walls arranged along said groove to decreasedepthwise in the direction opposite to rotation of said rotatablerunner, two adjoining said base walls disposed about a base shoulder,each said base shoulder locally redirects said longitudinal flow to forman outward radial flow in the direction of one said annular seal ring,said base walls bounded by and intersecting a pair of side walls, eachsaid side wall includes at least one side shoulder which narrows saidgroove widthwise and locally redirects said longitudinal flow away fromsaid side wall to form a lateral flow in the direction of the other saidside wall.
 2. The circumferential seal assembly of claim 1, wherein onesaid side shoulder along each said side wall intersects one said baseshoulder so that said outward radial flow and said lateral flowsinteract.
 3. The circumferential seal assembly of claim 1, wherein onesaid base shoulder disposed between a pair of said side shoulders alongeach said side wall.
 4. The circumferential seal assembly of claim 3,wherein two said side shoulders upstream of said base shoulder disposedin an opposed arrangement.
 5. The circumferential seal assembly of claim3, wherein two said side shoulders downstream of said base shoulderdisposed in an opposed arrangement.
 6. The circumferential seal assemblyof claim 3, wherein two said side shoulders upstream of said baseshoulder disposed in an offset arrangement.
 7. The circumferential sealassembly of claim 3, wherein two said side shoulders downstream of saidbase shoulder disposed in an offset arrangement.
 8. The circumferentialseal assembly of claim 1, wherein one said side shoulder along each saidside wall disposed upstream from said base shoulder.
 9. Thecircumferential seal assembly of claim 1, wherein one said side shoulderalong each said side wall disposed downstream from said base shoulder.10. The circumferential seal assembly of claim 1, wherein one said sideshoulder intersects said base shoulder.
 11. The circumferential sealassembly of claim 10, wherein said base shoulder disposed between twoother said side shoulders.
 12. The circumferential seal assembly ofclaim 11, wherein said two other said side shoulders disposed along onesaid side wall, said side shoulder disposed along another said side wallintersects said base shoulder.
 13. The circumferential seal assembly ofclaim 11, wherein one of said two other said side shoulders disposedalong the same said side wall as said side shoulder which intersectssaid base shoulder.
 14. The circumferential seal assembly of claim 1,wherein a depth of each of two said side shoulders are equal.
 15. Thecircumferential seal assembly of claim 1, wherein a depth of each of twosaid side shoulders differ.
 16. The circumferential seal assembly ofclaim 1, wherein a depth of each of one said side shoulder and one saidbase shoulder differ.
 17. The circumferential seal assembly of claim 1,wherein a depth of each of one said side shoulder and one said baseshoulder are equal.
 18. The circumferential seal assembly of claim 1,wherein at least one said base wall is tapered.
 19. The circumferentialseal assembly of claim 1, wherein at least one said side wall istapered.
 20. The circumferential seal assembly of claim 1, wherein saidbase walls and said side walls are tapered.
 21. A method for forming athin film between a pair of annular seal rings and a rotatable runnercomprising the steps of: (a) communicating a source flow into a feedgroove communicable with at least two grooves, each said groove has anupstream end at the intersection between said groove and said feedgroove and a downstream end; (b) separating said source flow at saidupstream ends into each said groove to form a longitudinal flow therein;(c) redirecting said longitudinal flow via interaction with a baseshoulder interposed between a pair of base walls to form an outwardradial flow adjacent to said base shoulder, said base walls disposedbetween a pair of side walls, said base walls arranged along said grooveto decrease depthwise in the direction opposite to rotation of saidrotatable runner; and (d) redirecting said longitudinal flow viainteraction with a side shoulder along at least one said side wall toform a lateral flow in the direction of another said side wall, saidlateral flow and said outward radial flow perpendicular to one anotherand to said longitudinal flow.
 22. The method of claim 21, furthercomprising the step of: (e) converging at least one said lateral flowwith said outward radial flow when at least one said side shoulderintersects said base shoulder whereby said side shoulder(s) and saidbase shoulder are aligned along a plane that traverses said groove, saidconverging step enhances the stiffness of a thin-film layer between onesaid annular seal ring and said rotatable runner.
 23. The method ofclaim 21, wherein at least one said lateral flow formed downstream fromsaid outward radial flow.
 24. The method of claim 21, wherein at leastone said lateral flow formed upstream from said outward radial flow. 25.The method of claim 21, further comprising the step of: (e) convergingsaid lateral flow from one said side wall with another said lateral flowfrom another said side wall when said side shoulders are disposed in anopposed arrangement whereby said side shoulders are aligned along aplane that traverses said groove, said converging step enhances thestiffness of a thin-film layer between one said annular seal ring andsaid rotatable runner.
 26. The method of claim 21, further comprisingthe step of: (e) impinging one said side wall by said lateral flowformed by said side shoulder along another said side wall, saidimpinging step enhances the stiffness of a thin-film layer between onesaid annular seal ring and said rotatable runner.